Chongming Island is the largest estuarine alluvial island in the world. It has a well-developed river network. In June 2018, trawl surveys on the fish were carried out in 16 fixed sampling sites in the representative rivers of Chongming Island, including the Nanheng Canal, Beiheng Canal and also the vertical canals Miaogang, Baozhengang, and Bayaogang. The composition and distribution characteristics of the fish communities in summer were analyzed based on these surveys. A total of 4417 specimens belonging to 6 orders, 9 families and 30 species of the fishes were collected in the surveys. Among them, 27 species were freshwater fish, 2 species were migratory fish and 1 species was coastal marine fish. And 20, 17 and 18 fish species were recorded in the Beiheng Canal, Nanheng Canal, and the vertical canals respectively. The characteristics of the fish assemblages, including the dominant species, varied among the rivers. The common dominant species of all the rivers were Carassius auratus, Pseudogramma simoni and Erythroculter ilishaeformis. Some species were only recorded in some specific reaches. The average species number, abundance and biomass of the fish in the Beiheng Canal were much higher than those in the Nanheng Canal and also the vertical canals, but there was no significant difference among the rivers (P>0.05). The average body length of major dominant species, Carassius auratus, Pseudogramma simoni and Erythroculter ilishaeformis in the Beiheng Canal were also the largest, and there was a very significant difference in individual body length between the Nanheng Canal and the Beiheng Canal (P<0.01). Cluster and nMDS analysis showed the greater difference between the fish assemblages in the Beiheng Canal and the Nanheng Canal, while those in the vertical canals were between these two. The results of ANOSIM also showed that the difference of the fish community structure between the Beiheng Canal and the Nanheng Canal was extremely significant (R=0.524, P=0.008), the average dissimilarity between these two groups appeared to be the highest at 43.92%, and there were 10 main species causing such difference (contribution rate was greater than 5%).In general, we found out that the community composition and distribution characteristics of the fish assemblages in the rivers of Chongming Island were different from those of general inland rivers, while had some characteristics of the estuarine islands. In the future, comprehensive studies on the community composition, distribution characteristics, developing trends and the corresponding mechanisms of the fishes in the rivers of Chongming Island should be carried out based on the long term monitoring.