Abstract: To understand the changing pattern of fish community diversity in the inland rivers of Chongming Island, Shanghai City, and its relationship with environmental factors, we collected fish samples from 16 sites in the inland rivers on Chongming Island in August(summer) and November(fall) 2021,investigated the environmental factors to analyze the structure of the fish community in the inland rivers in the summer and fall seasons and its relationship with environmental factors.A total of 47 species of fishes were collected in the field survey, which belonged to 7 orders, 12 families, and 40 genera, among which 61.70% were cyprinoids, 82.97% were freshwater fishes and 40.43% were omnivorous fishes.Carassius auratus,Coilia nasus,Culter dabryi,andPseudobrama simoniwere the dominant species.The study showed that the number of fish species in each sampling site varied from 6 to 18 species in summer and fall, with the richness indexDranging from 1.14 to 3.72,the diversity indexH′ ranging from 1.07 to 2.43,and the evenness indexJ′ ranging from 0.58 to 0.93.Cluster and NMDS results indicated that there was some spatial and temporal heterogeneity in the inland river fish community on Chongming Island.RDA showed that fish community structure was significantly associated with environmental factors such as water temperature, TP, BOD5,and pH.The study findings can provide scientific and technological references for the conservation of aquatic biodiversity in the Changjiang River estuary, and provide basic data for the evaluation of the effectiveness of the Changjiang River conservation.