Transgenic Bt cotton has been one of the most popular transgenic Bt crops in China. With increasing Bt cotton grown on arable soils, its impacts on soil environment have received more attentions due to the potential ecological risks by releasing Bt protein through root exudates, pollen or plant residue. A pot experiment was conducted under greenhouse conditions to investigate enzymatic and microbial activities in rhizosphere soils grown with Bt cotton (Sukang103) or with non-Bt cotton (Sumian12). The tested soil was a sandy loamy soil, collected from Yancheng, Jiangsu Province, China. A rhizobag made from nylon mesh was placed in the center of a plastic pot (D×H=30×30 cm) and used to separate rhizosphere from non-rhizosphere. All pots were arranged in a randomized complete block design with 4 replicates, and rearranged daily to minimize positional effects on growth. The pots were weighed and irrigated with distilled water daily to keep soil moisture at 80% field capacity. Soil samples were collected at seedling, squaring, flowering-boll and boll-opening stages, respectively, to measure soil respiration, microbial biomass C and activities of soil enzymes including sucrase, dehydrogenase, alkaline phosphatase, urease, and protease. Compared with control (non-transgenic Bt cotton), the activities of dehydrogenase, alkaline phosphatase, sucrase and microbial respiration were obviously affected by planting Bt cotton but varied with growth stages. No significant differences in soil urease, protease and microbial biomass C were observed between Bt cotton and non-Bt cotton during the growth period. Sucrase activity at seedling stage was significantly higher in rhizosphere soil grown with Bt cotton than in rhizosphere grown with non-Bt cotton (i.e. Bt cotton>non-Bt cotton, increased by 25.5%). Higher dehydrogenase activity and microbial respiration were detected in the soil with Bt cotton than with non-Bt cotton at flowering-boll stage (i.e. Bt cotton>non-Bt cotton, enhanced by 21.6% and 36.1%, respectively). Moreover, the activity of alkaline phosphatase was significantly lower in the soil with Bt cotton than with non-Bt cotton at both flowering and boll-opening stages (Bt cotton<non-Bt cotton, decreased by 22.1% and 32.9%, respectively). Further research, however, is needed to better evaluate the impacts of transgenic Bt cotton on soil eco-environment under field conditions.