In order to understand the fish community structure and diversity in the section near the Yangtse River estuary, the temporal and spatial characteristics of fish community structure, dominant species, quantity and biomass were investigated in 2017. The results showed that 62 species of fishes were collected, belonging to 8 orders 17 families. In terms of the ecological types, omnivore fish, sedentary fish and demersal fish were dominant. In terms of fish catching specifications, small-sized fishes (<50 g) were dominant in quantity and species (67.77% and 37), and quantity of fishes with average mass less than 50 g was 59.68% and 37.59%.Analysis of the diversity index showed that: the range of Margalef index(D) was 3.73 to 6.26, Shannon-Wiener index(H') was 2.44 to 2.98, Simpson index(C) was 0.07 to 0.15 and Pielou index(E) was 0.64 to 0.76, and the average value of them was 5.03,2.62,0.12 and 0.73. As a whole, the community diversity index in spring and summer was higher than that in autumn and winter; the community diversity index in Changshu sampling site was higher than that in Nantong sampling site. Significant seasonal variations showed that fish quantity was highest in summer and lowest in winter. The clustering results showed that the fish community was divided into 2 groups when the similarity was 44.34%. Community differences are mainly due to the seasonal variation. The research supplemented the basic data of fish and provided a scientific basis for the assessment and protection of fishery resources in Yangtze River basin.