Abstract: To evaluate effects of tunnel construction on the sediment bacterial community and diversity in Lake East, 19 sampling points were selected and analyzed for 3 consecutive time points during the construction process. The PCRDGGE and molecular cloning were applied to analyze the bacterial species composition, community and diversity of all sampling sediment. A total of 18 bacterial genera belonging to 5 phyla, 17 bacterial genera belonging to 6 phyla and 11 bacterial genera belonging to 5 phyla were identified from 3 different batches of sediment samples, respectively. At the level of phylum, Proteobacteria was predominant bacteria among all three batches, but its percentage among the total diversity was decreased with the tunnel construction, presenting 86%, 80.6% and 43.9%, respectively. At the level of genera, Escherichia/Shigella was predominant bacteria at the first sampling while Steroidobacter at the third sampling. Attheearly stage of tunnel construction, bacterial community structure of the middle area of Lake Tangling and Lake Guozheng were similar at the level of genus, which was significantly different from those of Lake Tuan. The effect of tunnel construction on the sediment bacterial community was distance dependent. The bacterial community of the temporarily producing closed area for tunnel construction was remarkably different from that of open water area, although both contain Escherichia/Shigella. However, the community diversity and composition of the middle area of Lake Tangling, Lake Guozheng and Lake Tuan became similar at the late stage of tunnel construction. The distance dependent effect of tunnel construction on the bacterial community was not significant at the late stage of tunnel construction. Additionally, temporarily forming closed area was similar to open water area regarding their sediment bacterial community composition. During the construction, the highest diversity index of bacterial community for all three batches of samples appeared in the sampling point adjacent the tunnel. The Simpson_1-D index, Shannon_H index and Margalef index gradually increased with the tunnel construction. Therefore, our results indicated that the tunnel construction had a remarkable influence on the bacterial community and diversity of Lake East sediment, although the long-term effect should be further evaluated.