166




                                  EXHIBIT 32.1
                                  ------------



           This is an Exhibit to the Form 20-F of Sinovac Biotech Ltd.
           -----------------------------------------------------------


                     Attached find the following materials:


              Certification of Weidong Yin pursuant to Section 906
              ----------------------------------------------------
                        of the Sarbanes-Oxley Act of 2002
                        ---------------------------------


                               End of Exhibit 32.1

                                   -----------






                                       167




                            CERTIFICATION PURSUANT TO
                             18 U.S.C. SECTION 1350,
                             AS ADOPTED PURSUANT TO
                  SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with the Annual Report on Form 20-F for fiscal year ended December
31, 2003 of Sinovac Biotech Ltd., a company  organized under the laws of Antigua
and  Barbuda  (the  "Company"),  as  filed  with  the  Securities  and  Exchange
Commission on the date hereof (the "Annual Report"),  I, Weidong Yin,  President
and Chief  Executive  Officer  of the  Company  certify,  pursuant  to 18 U.S.C.
Section  1350 as adopted  pursuant to Section 906 of the  Sarbanes-Oxley  Act of
2002, that:

1.   The Annual Report fully complies with the  requirements of Section 13(a) or
     15(d) of the Securities Exchange Act of 1934, as amended; and

2.   The  information  contained in the Annual  Report fairly  presents,  in all
     material respects, the financial condition and results of operations of the
     Company.


Dated: June 30, 2004                    /s/ Weidong Yin
                                        ----------------------------------------
                                        Weidong Yin, President, CEO and Director