In order to investigate the species composition and diversity of larvae and juvenile fish in Chongming Dongtan and its surrounding waters, 14 stations were set up in Chongming Dongtan and its surrounding waters from November 2020 to August 2021, and surface horizontal trawling surveys were conducted quarterly with large larvae and juvenile fish nets (diameter 1.3 m, mesh 0.5 mm) for four voyages at each station. A total of 4 556 larvae and juveniles were collected, belonging to 8 orders, 14 families and 48 species. The species composition of dominant species is obvious, of which Coilia mystus (25.09%) was the dominant fish. This was followed by Stolephorus commersonnii (20.12%) and Salanx ariakensis (17.11%). The results showed that the species number and density of larvae and juvenile fishes in spring and summer were significantly higher than those in autumn and winter, and the highest density was 0.658 ind./m³ in summer. The number of species in spring was 28, and the number of species in winter was the least. The species richness index, diversity index and evenness index showed the same trend between seasons, with the highest in spring and the lowest in winter. The density of larvae and juveniles was higher in the north branch than in the south branch in spring and summer, and higher in the south branch than in the north branch in autumn and winter. The results of cluster analysis showed that larvae and juvenile fishes can be divided into freshwater group, estuarine group Ⅰ and estuarine group Ⅱ in spring. Summer can be divided into estuarine group and marine group. the larvae and juveniles in Chongming Dongtan of Yangtze River estuary in autumn could be divided into freshwater group, estuarine group and marine group. The species and number of fish larvae and juveniles in winter are very small. Pearson correlation index analysis showed that the richness index, diversity index and evenness index in summer were correlated with salinity, but not with water temperature. The temporal and spatial distribution characteristics of dominant species and communities of larvae and juvenile fish in Chongming Dongtan and the environmental factors affecting their distribution were also discussed. The results will provide important analysis data for the sustainable development and protection of fishery ecological resources in Chongming Dongtan, Yangtze River Estuary.