Abstract: Benthic macroinvertebrates assemblages were collected from 29 sites in the upper reaches of the Taihu Lake watershed,i.e.the Nanhe,Yunnan,Yunbei and Taoge water systems,in Changzhou area of China in 2003.A total of 113 species were found including 18 species in Gastropoda,10 speices in Lamellibranchia,8 species in Oligochaeta,4 species in Hirudinea,6 species in Crustacean and 67 species in Insecta,with Limnodrilus hoffmeisteri and Bellamya purificata being the dominant species.The average density of the communities was 658 m^-2 with L.hoffmeisteri being the highest,i.e. 400 m^-2.Among the 29 sampling sites,Guanshanqiao was the highest in benthic macroinvertebrate diversity and its species richness,Shannon-Wiener diversity,evenness and ecological dominant index was 54,4.36,0.76 and 0.08,respectively.In terms of benthic macroinvertebrate diversity,the 4 water systems were in the order of Nanhe>Taoge>Yunnan>Yunbei.CCA analysis of the 24 species that were more than 15% in occurrence frequency and 6 environmental factors showed that total nitrogen,total phosphorus and dissolved oxygen were the major factors influencing distribution of benthic macroinvertebrates in the research area.

Key words: benthic macroinvertebrate, diversity, Taihu Lake watershed, Changzhou