[Aim] We evaluated the effect of transgenic Cry1Ac/1Ab cotton on the development and predation function of Harmonia axyridis.[Method] H.axyridis larvae were fed with Helicoverpa armigera that have been fed on either Cry1Ac/1Ab cotton (A26-5 variety) or its parental conventional cotton (J14 variety).[Result] Compared with the conventional parental cotton, the time from the first to the pupal stage larvae of the H. axyridis which were fed with the larvae of the H.armigera that had been fed on transgenic cotton leaves were prolonged by 0.77 days, but the difference was not significant. The body weights instar larvae did not significantly differ between both feeds. The 1st to 4th instar larvae of the H. axyridis had great predation ability with the increase of the density of H. armigera, predation function response consistent with the Holling Ⅱ model.[Conclusion] The transgenic Cry1Ac/1Ab cotton had no significant effect on the growth and development of H. axyridis, and there was no significant difference in predation function between the two cotton varieties.