【Background】The environmental safety assessment of transgenic crop is required before its commercial cultivation． In this study, we used the assessment of transgenic crop and investiged the effects to cotton arthropod species richness in cotton fields. 【Method】We compared the plant height, leaf number of main stem, the content of chlorophyll, specific leaf area, fruit branch number, boll number and other growth parameters in the field of the Cry1Ac+Cry2Ab transgenic cotton during May to September in 2014 as well as in transgenis Cry1Ac cotton CCRI 41 and non-transgenic cotton variety CCRI 49 fields for comparison. At the same time, the species richness of arthropod community in cotton fields was systematic surveyed during the second, third and fourth generation of cotton bollworm occurrence. 【Result】The growth potential was no different between transgenic Cry1Ac+Cry2Ab cotton, transgenic Cry1Ac cotton and non-transgenic cotton. In terms of arthropod community, the target pest Helicoverpa armigera was obviously controlled,but there was no influence of transgenic Cry1Ac+Cry2Ab cotton on other sucking pests and natural enemies,such as cotton aphids, cotton thrips, Bemisia tabaci, Lygus lucorum, Propylaea japonica, Erigonidium graminicola, lacewings and Orius. 【Conclusion and significance】Transgenic Cry1Ac+Cry2Ab cotton has no competitive advantage against the other cotton crops, but plants traits were better than the other cotton crops. No obvious effects on the arthropod species richness in cotton fields were observed. The study supports the ideas that transgenic Cry1Ac+Cry2Ab cotton is relatively safe.