Abstract: Insecticidal activity of different organs of transgenic corn expressing Cry1Ab insecticidal protein gene from B acillus thuringiensis(Bt) to H elicoverpa armigera was tested inlaboratory. The results showed that popcorn has the lowest activity among the 7 organs of Bt corn, and the order of insecticidal activity was as follows: popcorn < filament < stem < corncob < bract < corn-grain < leaf. There was significant difference of insecticidal activity of filament to Cry1Ac-resistant population (13.1-fold of resistance ratio) compared with that of a susceptible population of the pest.