Abstract:By feeding Spodoptera exigua Hübner (Lepidoptera:Noctuidae) with the mature leaves of transgenic Bt cotton GK22, transgenic Bt+CpTI cotton SGK321 and their conventional cottons SM3 and Shiyuan321, the influences of different cotton cultivars on the survival rate, fecundity and index of population trend(I)of three continuous generations of the beet armyworm was carried out. Results indicated that the influences of two transgenic cottons were significance on survival rate, fecundity and index of population trend(I), but the influences gradually become lower following the feed time lengthened. The laboratory population life table of the three continuous generations of the beet armyworm showed that the index of population trend (I)of the three generations fed with SM3 was 43.74, 135.72, 141.17 respectively, the I value fed with GK22 was 14.89, 82.46, 110.24 respectively, the I value fed with Shiyuan321 was 51.63, 89.57, 128.90 respectively, and the I value fed with SGK321 was 43.26, 81.37, 114.66 respectively. It indicated that followed by prolonging feed time, population increasing become quicker and quicker, and the increased differences between transgenic cottons and its conventional cottons also become no significant.