Abstract: The Three Gorges Reservoir on the Yangtze River of China is the largest hydropower project in the world. Three reaches from the upper Yangtze River were selected for the study on the effect of distance from the dam on river fish community structure and fish composition trends. A total of 8680 fish representing 58 species of 11 families were collected during the study period from November 2010 to October 2011. The results indicated that the fish assemblage in the reservoir was dominated by Cyprinids. Fish abundance in the summer was significantly higher than that in other seasons (P0.05). Fish species richness and abundance close to the dam (Zigui reach) were less, comparatively higher at the middle reach (Wanzhou reach) and intermediate at far from the dam (Fuling reach). Fish fauna shifted from lotic species to lentic species associated with reservoir construction. Therefore, it is evident that impoundment of the Three Gorges Reservoir has altered the fish assemblage structure, and fish species compositions have shifted in their relative abundance over time.