Abstract: The species composition, relative abundance and spatial distribution of alien fish were studied in 8 typical sections of the Three Gorges Reservoir from April to June and November to December 2020. The results showed that: (1)There were 108 species of fish in the main and tributary streams of the Three Gorges Reservoir area, belonging to 8 orders and 21 families, of which 16 species were alien fish, accounting for 14.81% of the total number of fish species collected. (2)The alien fish, Coilia brachygnathus, Neosalanx taihuensis, Oreochromis niloticus, were dominant species. Except Wujiang River, Coilia brachygnathus was the dominant species in other seven sampling sections, and the relative dominance were 2.05%-18.71%; In the tributaries of Xiaojiang River and Daning River, Neosalanx taihuensis was the dominant species, with a relative dominance of 2.83% and 8.39%, respectively; Oreochromis niloticus was the dominant species only in the Xiaojiang River, with a relative dominance of 1.56%. (3)The relative abundance of alien fish in the main stream was significantly lower than that in the tributary, and the weight percentage of alien fish in the tributary of Xiaojiang was the highest, 12.30%; the abundance percentage of alien fish in the tributary of Daning was the highest, 57.55%. In view of results, to avoid the possible impact of alien fish on fish resources in the Three Gorges Reservoir, the comprehensive control measures were proposed to manage and control the population of alien fish.