Abstract: Effects of Bt toxin on the development and fecundity of Chrysopa sinica Tjeder fed on Aphis gossypii Glover reared on three cotton varieties (Simian-3，GK-12 and 99B)and on mixed Aphis gossypii were studied in laboratory．The results show that the mortalities of larva and cocoon，the percentage of adult achievement have no significant differences among these four treatments．When larva fed on mix aphides，its development time is significantly shorter than that fed on Simian-3 or GK-12 aphid，and also shorter than that fed on 99B aphid．There is no significant influence when Chrysopa sinica fed on either Simian-3 and GK-12 or 99B aphid．When Chrysopa sinica fed on 4 treatm ents aphides ，there are no significant differences among their develc pmental time，cocoon weight，and sex ratio of adult．Aphis gossypii reared on Bt cotton have no detrim ental effect on prexM positing and oviposition time of it．But Chryso perla fem ale adult fed on 99B and mixed aphides can lay significantly more eggs，and its lifespan is significantly longer than that fed on Simian-3 or GK-12．There is no phenomenal influence on percentage hatched eggs either their parental larva fed on Simian-3，GK-12 or 99B aphides ．When the mixed aphides are given to the parental larva of Chryso perla， the hatching rate is sign ificantly lower than that fed on Simiam-3，GK-12 or 99B aphid．