<PAGE>   1
             As filed with the Securities and Exchange Commission on May 4, 2000
                                                 Registration No. 333-__________
================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                ----------------

                                    FORM S-8

                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

                                ----------------

                                    SINA.COM
             (Exact name of Registrant as specified in its charter)

         CAYMAN ISLAND                                          52 - 2236363
 (State or other jurisdiction                                (I.R.S. Employer
     of incorporation)                                      Identification No.)

                     VICWOOD PLAZA, UNITS 01-03, 18TH FLOOR,
                               199 DES VOEUX ROAD
                               CENTRAL, HONG KONG
                    (Address of principal executive offices)

                             -----------------------

                           SINANET.COM 1997 STOCK PLAN
                  SRS INTERNATIONAL LTD. 1997 STOCK OPTION PLAN
                            SINA.COM 1999 STOCK PLAN
                       SINA.COM 1999 EXECUTIVE STOCK PLAN
                   SINA.COM 1999 DIRECTORS' STOCK OPTION PLAN
                   SINA.COM 1999 EMPLOYEE STOCK PURCHASE PLAN
                            (Full title of the Plans)

                             -----------------------

                       VICTOR LEE, CHIEF FINANCIAL OFFICER
                                    SINA.COM
                                1313 GENEVA DRIVE
                           SUNNYVALE, CALIFORNIA 94089
                                 (408) 548-0000

 (Name, address and telephone number, including area code, of agent for service)

                             -----------------------
                                    Copy to:

                                  Tae Hea Nahm
                                Venture Law Group
                           A Professional Corporation
                               2800 Sand Hill Road
                          Menlo Park, California 94025
                                 (650) 854-4488

                                Page 1 of 9 Pages
                             Exhibit Index on Page 7
               (Calculation of Registration Fee on following page)


<PAGE>   2


<TABLE>
<CAPTION>
--------------------------------------------------------------------------------------------------------------------------------
                                                 CALCULATION OF REGISTRATION FEE
--------------------------------------------------------------------------------------------------------------------------------

                                                                             Proposed             Proposed
                                                                             Maximum               Maximum 
                                                           Maximum           Offering             Aggregate          Amount of
                                                         Amount to be          Price               Offering         Registration
Title of Securities to be Registered                    Registered (1)       Per Share              Price               Fee
--------------------------------------------------------------------------------------------------------------------------------
<S>                                                   <C>                    <C>                <C>                 <C>       
Sinanet.com 1997 Stock Plan
     Ordinary Share, $0.133 par value ..........      499,958 shares         $     0.24(2)      $    119,989.92      $    31.68


SRS International Ltd. 1997 Stock Option Plan
     Ordinary Share, $0.133 par value ..........      257,464 shares         $     0.16(2)      $     41,194.24      $    10.88


SINA.com 1999 Stock Plan
     Ordinary Share, $0.133 par value ..........      2,189,548 shares       $     6.10(2)      $ 13,356,242.80      $ 3,526.05
     Ordinary Share, $0.133 par value ..........      2,496,660 shares       $    18.00(3)      $ 44,939,880.00      $11,864.13

SINA.com 1999 Executive Stock Plan
     Ordinary Share, $0.133 par value ..........      1,614,511 shares       $     7.33(2)      $ 11,834,365.63      $ 3,124.27
     Ordinary Share, $0.133 par value ..........      579,239 shares         $    18.00(3)      $ 10,426,302.00      $ 2,752.54

SINA.com 1999 Directors' Stock Option Plan
     Ordinary Share, $0.133 par value ..........      187,500 shares         $    17.00(2)      $  3,187,500.00      $   841.50
     Ordinary Share, $0.133 par value ..........      562,500 shares         $    18.00(3)      $ 10,125,000.00      $ 2,673.00

SINA.com 1999 Employee Stock Purchase Plan
     Ordinary Share, $0.133 par value ..........      3,750,000 shares       $    15.30(4)      $ 57,375,000.00      $15,147.00

--------------------------------------------------------------------------------------------------------------------------------

             TOTAL                                    12,137,380 shares                         $151,405,474.59      $39,971.05
                                                      -----------------                         ---------------      ----------
</TABLE>


-----------------------

(1)     This Registration Statement shall also cover any additional shares of
        Ordinary shares which become issuable under any of the Plans being
        registered pursuant to this Registration Statement by reason of any
        stock dividend, stock split, recapitalization or any other similar
        transaction effected without the receipt of consideration which results
        in an increase in the number of the Registrant's outstanding ordinary
        shares.

(2)     Computed in accordance with Rule 457(h) under the Securities Act of 1933
        solely for the purpose of calculating the registration fee. Computation
        based on the weighted average per share exercise price (rounded to
        nearest cent) of outstanding options under the referenced plan, the
        shares issuable under which are registered hereby.

(3)     Estimated in accordance with Rule 457(h) under the Securities Act of
        1933 solely for the purpose of calculating the registration fee. The
        computation with respect to unissued options is based upon the average
        ask and bid prices of ordinary shares as reported on the Nasdaq National
        Market on April 27, 2000.

(4)     Estimated in accordance with Rule 457(h) under the Securities Act of
        1933 solely for the purpose of calculating the registration fee. The
        computation is based on the average ask and bid prices of ordinary
        shares as reported on the Nasdaq National Market on April 27, 2000,
        multiplied by 85%, which is the percentage of the trading purchase price
        applicable to purchases under the referenced Plan.



                                      -2-

<PAGE>   3

                                     PART II
               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

Item 3. INCORPORATION OF DOCUMENTS BY REFERENCE.

        The following documents filed with the Securities and Exchange
Commission (the "Commission") are hereby incorporated by reference:

        (a) The Registrant's Prospectus filed on April 12, 2000 pursuant to Rule
424(b) of the Securities Act, which contains audited financial statements for
the Registrant's latest fiscal year for which such statements have been filed.

        (b) Not Applicable.

        (c) The description of the Registrant's Ordinary shares contained in the
Registrant's Registration Statement on Form 8-A filed with the Commission under
Section 12 of the Securities Exchange Act of 1934 (the "Exchange Act") on April
12, 2000, including any amendment or report filed for the purpose of updating
such description.

        All documents subsequently filed by the Registrant pursuant to Sections
13(a), 13(c), 14 and 15(d) of the Exchange Act, prior to the filing of a
post-effective amendment which indicates that all securities offered hereby have
been sold or which deregisters all securities then remaining unsold, shall be
deemed to be incorporated by reference in this Registration Statement and to be
part hereof from the date of filing such documents.

Item 4. DESCRIPTION OF SECURITIES. Not applicable.

Item 5. INTERESTS OF NAMED EXPERTS AND COUNSEL.

        Certain legal matters with respect to the legality of the issuance of
the ordinary shares registered hereby will be passed upon for the Registrant by
Venture Law Group in Menlo Park, California. As of the date of this Registration
Statement, attorneys of Venture Law Group shares and an investment partnership
associated with Venture Law Group own 41,205 shares of the Company's ordinary
shares.

Item 6. INDEMNIFICATION OF DIRECTORS AND OFFICERS.

        Cayman Islands law does not limit the extent to which a company's
articles of association may provide for indemnification of officers and
directors, except to the extent any such provision may be held by the Cayman
Islands courts to be contrary to public policy, such as to provide
indemnification against civil fraud or the consequences of committing a crime.
The Registrant's Articles of Association provide for indemnification of officers
and directors for losses, damages, costs and expenses incurred in their
capacities as such, except if they acted in a willfully negligent manner or
defaulted in any action against them. In addition, the Registrant has entered
into Indemnification Agreements with our directors and officers.

        Insofar as indemnification for liabilities arising under the Securities
Act may be permitted to directors, officers or persons controlling the
registrant pursuant to the foregoing provisions, we have been informed that in
the opinion of the Securities and Exchange Commission such indemnification is
against public policy as expressed in the Securities Act and is therefore
unenforceable as a matter of U.S. law.

        At present, there is no pending litigation or proceeding involving any
director, officer, employee or agent of the Company where indemnification will
be required or permitted. The Company is not aware of any threatened litigation
or proceeding that might result in a claim for such indemnification.



                                      -3-

<PAGE>   4

Item 7. EXEMPTION FROM REGISTRATION CLAIMED. Not applicable.

Item 8. EXHIBITS.


<TABLE>
<CAPTION>
        Exhibit
        Number
        -------
<S>                 <C>
        5.1         Opinion of Venture Law Group, a Professional Corporation.

        23.1        Consent of Venture Law Group, a Professional Corporation
                    (included in Exhibit 5.1).

        23.2        Independent Auditors' Consent (see p. 9).

        24.1        Powers of Attorney (see p. 6).
</TABLE>


Item 9. UNDERTAKINGS.

        The undersigned Registrant hereby undertakes:

               (1) to file, during any period in which offers or sales are being
made, a post-effective amendment to this registration statement to include any
material information with respect to the plan of distribution not previously
disclosed in the registration statement or any material change to such
information in the registration statement.

               (2) that, for purposes of determining any liability under the
Securities Act, each such post-effective amendment shall be deemed to be a new
registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

               (3) to remove from registration by means of a post-effective
amendment any of the securities being registered which remain unsold at the
termination of the offering.

        The undersigned Registrant hereby undertakes that, for purposes of
determining any liability under the Securities Act, each filing of the
Registrant's annual report pursuant to Section 13(a) or Section 15(d) of the
Exchange Act that is incorporated by reference in the registration statement
shall be deemed to be a new registration statement relating to the securities
offered therein, and the offering of such securities at that time shall be
deemed to be the initial bona fide offering thereof.

        Insofar as the indemnification for liabilities arising under the
Securities Act may be permitted to directors, officers and controlling persons
of the Registrant pursuant to the foregoing provisions, or otherwise, the
Registrant has been advised that in the opinion of the Commission such
indemnification is against public policy as expressed in the Securities Act and
is, therefore, unenforceable. In the event that a claim for indemnification
against such liabilities (other than the payment by the Registrant of expenses
incurred or paid by a director, officer or controlling person of the Registrant
in a successful defense of any action, suit or proceeding) is asserted by such
director, officer or controlling person in connection with the securities being
registered hereunder, the Registrant will, unless in the opinion of its counsel
the question has already been settled by controlling precedent, submit to a
court of appropriate jurisdiction the question of whether such indemnification
by it is against public policy as expressed in the Securities Act and will be
governed by the final adjudication of such issue.

                            [Signature Pages Follow]



                                      -4-

<PAGE>   5

                                   SIGNATURES

        Pursuant to the requirements of the Securities Act of 1933, the
Registrant, SINA.com, a corporation organized and existing under the laws of
Cayman Islands, certifies that it has reasonable grounds to believe that it
meets all of the requirements for filing on Form S-8 and has duly caused this
Registration Statement to be signed on its behalf by the undersigned, thereunto
duly authorized, in the City of Sunnyvale, State of California, on May 4, 2000.

                                   SINA.com


                                   By:  /s/  Victor Lee
                                        ----------------------------------------
                                        Victor Lee
                                        Chief Financial Officer



                                      -5-

<PAGE>   6

                                POWER OF ATTORNEY

        KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature
appears below constitutes and appoints Victor Lee and Charles Chao, jointly and
severally, his or her attorneys-in-fact and agents, each with the power of
substitution and resubstitution, for him or her and in his or her name, place or
stead, in any and all capacities, to sign any amendments to this Registration
Statement on Form S-8, and to file such amendments, together with exhibits and
other documents in connection therewith, with the Securities and Exchange
Commission, granting to each attorney-in-fact and agent, full power and
authority to do and perform each and every act and thing requisite and necessary
to be done in and about the premises, as fully as he or she might or could do in
person, and ratifying and confirming all that the attorneys-in-fact and agents,
or his or her substitute or substitutes, may do or cause to be done by virtue
hereof.

        Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed by the following persons in the
capacities and on the dates indicated.



<TABLE>
<CAPTION>
          Signature                          Title                              Date
          ---------                          -----                              ----
<S>                            <C>                                         <C>

/s/  Daniel Chiang
----------------------------
Daniel Chiang                  Chairman of the Board                       April 24, 2000

/s/  Zhidong Wang
----------------------------
Zhidong Wang                   Chief Executive Officer and President       April 24, 2000
                                 (Principal Executive Officer)

/s/  Victor Lee
----------------------------
Victor Lee                     Chief Financial Officer                     April 24, 2000
                                 (Principal Financial Officer)

/s/  Charles Chao
----------------------------
Charles Chao                   Vice President, Finance                     April 24, 2000
                                 (Principal Accounting Officer)

/s/  Pehong Chen
----------------------------
Pehong Chen                    Director                                    April 24, 2000

/s/  Yongji Duan
----------------------------
Yongji Duan                    Director                                    April 24, 2000

/s/  Yoshitaka Kitao
----------------------------
Yoshitaka Kitao                Director                                    April 24, 2000

/s/  Lip-Bu Tan
----------------------------
Lip-Bu Tan                     Director                                    April 24, 2000

/s/  Ter Fung Tsao
----------------------------
Ter Fung Tsao                  Director                                    April 24, 2000
</TABLE>




                                      -6-

<PAGE>   7

                                INDEX TO EXHIBITS



<TABLE>
<CAPTION>
   Exhibit                                                                 Page
    Number                                                                  No.
    ------                                                                ------
<S>           <C>                                                         <C>
     5.1      Opinion of Venture Law Group, a Professional Corporation        8

     23.1     Consent of Venture Law Group, a Professional Corporation        8
              (included in Exhibit 5.1)

     23.2     Consent of Independent Accountants                              9

     24.1     Powers of Attorney                                              6
</TABLE>







<PAGE>   1

                                                                     Exhibit 5.1



                                   May 3, 2000



SINA.com
1313 Geneva Drive
Sunnyvale, CA 94089

        Registration Statement on Form S-8

Ladies and Gentlemen

        We have examined the Registration Statement on Form S-8 (the
"Registration Statement") filed by you with the Securities and Exchange
Commission (the "Commission") on or about May 4, 2000 in connection with the
registration under the Securities Act of 1933, as amended, of an aggregate of
499,958 ordinary shares pursuant to Sinanet.com 1997 Stock Plan, 257,464
ordinary shares pursuant to SRS International Ltd. 1997 Stock Option Plan,
4,686,208 ordinary shares under SINA.com 1999 Stock Plan, 2,193,750 ordinary
shares under SINA.com 1999 Executive Stock Plan, 750,000 ordinary shares under
SINA.com 1999 Directors' Stock Option Plan, and 3,750,000 ordinary shares under
SINA.com 1999 Employee Stock Purchase Plan (collectively the "Shares"). As your
counsel in connection with the Registration Statement, we have examined the
proceedings taken and are familiar with the proceedings proposed to be taken by
you in connection with the sale and issuance of the Shares.

        It is our opinion that upon conclusion of the proceedings being taken or
contemplated under the Plans or by us, as your counsel, to be taken
 prior to the
issuance of the Shares, and upon completion of the proceedings being taken in
order to permit such transactions to be carried out in accordance with the
securities laws of the various states where required, the Shares when issued and
sold in the manner described in the Registration Statement will be legally and
validly issued, fully paid and non-assessable.

        We consent to the use of this opinion as an exhibit to the Registration
Statement and further consent to the use of our name wherever appearing in the
Registration Statement, including the Prospectus constituting a part thereof,
and in any amendment thereto.

                                             Sincerely,

                                             VENTURE LAW GROUP
                                             A Professional Corporation

                                             /s/  Tae Hea Nahm

                                             Tae Hea Nahm




<PAGE>   1

                                                                    EXHIBIT 23.2



                       CONSENT OF INDEPENDENT ACCOUNTANTS

        We hereby consent to the incorporation by reference in the Registration
Statement on Form S-8 of SINA.com. of our report dated November 12, 1999, except
for Note 12, as to which the date is March 17, 2000, appearing in the Company's
Registration Statement on Form-1 ( No. 333-11718).

/s/ PricewaterhouseCoopers LLP
------------------------------
PricewaterhouseCoopers LLP

San Jose, California
May 3, 2000