A laboratory experiment for studying the effects of sediment dredging on microbial activity and functional diversity of mi-crobial community of sediments was carried out through one year. Using incubation of undredged(control) and dredged cores, wefound that dredging the upper 30cm layer of sediment remarkably affected physico-chemical and microbial characteristics of sedi-menu in the study area of Meiliang Bay, Lake Taihu. The microbial activity in dredged sediments was significantly lower(P<0.05)than that in undredged sediments. Sediment dredging affected considerably microbial activity in sediments, and the microbi-al activity in dredged sediments could not recovery in one year experiment. Sediment dredging also affected the functional diversityof microbial community in sediment, the diversity index of microbial community in early dredged sediments was significantly lower(P<0.05) than that in undredged sediments. Sediment dredging modified the community composition of sediment microbial eco-system and resulted in decreasing of diversity of microbial community. Sediment dredging affected microbial activity and functionaldiversity of microbial community, which consequently affected the cycling of biogenic elements in sediments.