The role of transgenic Bt cotton in integrated insect Pest management 'was studied in 1994-1998 period at laboratory, cage and field from the standpoint of blonomics, population ecology, community ecology and Integrated pest management. Bt cotton was highly resistant to cotton bollworm (Helicoverpa armigera) but the degree of its resistance fluctuated both in time and space; and the effects covered the pest's survival, development, reproduction and behavior. The bollworm was no longer the key pest of Bt cotton, but the red spider mites (Tetranychus cinnabrinus) aphids (Aphis gossipii) and thrips (Thrips tabaci) became the main ones. The dominant predator species had little change but the number of dominant: parasitoids of the bollworm decreased significantly. The diversity index (2.8023) and evenness (0.5805) in spring planted Bt cotton intercropped with wheat>single spring planted Br cotton (2.6133 and 0.5321, respectively)> short-season Bt cotton (1.8181 and 0.4082, respectively), but the dominant concentration index showed contrary result (0.1085, 0.1291 and 0.3360, respectively), thus the insect community of spring Bt cotton Intercropped with wheat was more stable. There vas no need for chemical control of the second generation of the bollworm. The threshold of third generation was 20-25 of 2nd-3rd instar larvae per 100 being 2-3 told of the conventional cotton. The toxin tolerance of the bollworm was apparently increased due to continuous cultivation of Bt cotton. Compared with the conventional cotton, the usage of insecticide in St car-ton was decreased by 60-80Z, and number of predators increased by 24.OZ, bringing about great economical, social and ecological profits.