【Background】Ammoniaoxidizing bacteria are the key microbes that catalyse nitrification, and the diversity of ammoniaoxidizing bacterial community has important influence on the transformation of nitrogen in soil. The cultivation of genetically modified plants may have the potential to alter the diversity of microbial community in soil through root exudates and plant residues. 【Method】 In this study, one event of cry1Ac/cpti transgenic rice (GM) and it′s parental nontransgenic rice (CK) was planted in the same field site for four consecutive years. The community composition and abundance of ammoniaoxidizing bacteria in paddy soil were assessed by denaturing gradient gel electrophoresis (DGGE) and realtime polymerase chain reaction (rtPCR) based on the 16S rRNA gene in the third and forth year after establishment of the experimental field site. 【Result】The results of redundancy discriminate analysis based on DGGE bands showed that composition of ammoniaoxidizing bacterial community markedly （P=0.〖KG-*8〗002，0.〖KG-*8〗018）changed during rice growth seasons in the third and forth year after establishment of the experimental field site, while no significant differences were observed in community composition of ammoniaoxidizing bacteria between fields with GM and CK, and the Shannon index of ammoniaoxidizing bacterial community in field with GM was similar to that of the nontransgenic control. Compared with nontransgenic plants, the abundance of 16S rRNA gene of ammoniaoxidizing bacteria in paddy soil with cry1Ac/cpti transgenic rice had no changes during rice growth in the third and forth year after establishment of the experimental field site, while it showed large seasonal changes, and was highest （P<0.〖KG-*8〗05） in the heading stage of rice. 【Conclusion and significance】Our field study indicates that the composition and abundance of ammoniaoxidizing bacterial community in paddy soil change with the growth of rice, but the cry1Ac/cpti transgenic rice had no large effect on either the composition or the abundance of ammoniaoxidizing bacterial community in paddy soil during rice growth at least in the short term.