Almost all insect-resistant genes applied in China is Cry1Ab/c and the resistance risk is increasing. Cry5Aa insect-resistant gene was synthesized according to the codon preference of cotton, it is transformed through pollen tube pathway into cotton plants, and it is identified through Kanamycin test, PCR and insect resistance test for different generation in the paper. The main results are shown as following: Firstly, transgenic plants of Cry5Aa were gotten successfully by pollen tube pathway method, and gene transformation efficiency of T1generation, T2 generation T3 generation was 7.76%, 73.1%, 95.5%, respectively. Secondly, results of identification of PCR showed that the positive rate of transgenic plants in T1 generation, was 2.35%, and 55.8% in T2 generation. Thirdly, corrected mortality rates of second, third and fourth generation of cotton bollworm for these transgenic plants was 85.42%, 75.35% and 62.79%, respectively, and the difference between these Cry5Aa insect-resistant transgenic plants and GK19 is not significant. Lastly, all above results indicate that Cry5Aa Bt can replace the current insect-resistant genes, and it is an ideal source for bollworm resistance.