Fish stock serve as the foundation for fishery development and the stability of ecosystems, identify the distribution characteristics of fish community assembly , which plays crucial role in the conservation and management of fishery resources and the maintenance of ecological functions. Our study focused on the characteristics of fish community assembly and similarity in nearshore waters Hainan Island, conducted two bottom trawl surveys in August and November 2024, and used a combination of statistical methods, including one-way ANOVA, Permutational Multivariate Analysis of Variance (PERMANOVA ), and Principal Coordinates Analysis (PCoA), to analysis the differences in species composition, dominant groups, and resource status of fish communities in different regions in nearshore waters of Hainan Island. The results showed that total of 451 species of fish were collected,, and the 288 species in the eastern Qionghai-Sanya waters are highest. The number of species in November is higher than that in August. S?rensen's dissimilarity index divides composition of fish in nearshore waters of Hainan Island into the southeastern Wenchang, Qionghai-Wanning, and Lingshui-Qiongsanya waters; the western Ledong, Changjiang-Dongfang, and Danzhou-Linggao waters; and the northern Qionghzhou Straits and Mulantou waters. The high abundance of fish stock are the western Changjiang-Ledong Sea (22036 ind./km2, 536.8 kg/km2) and the eastern Qionghai-Sanya Sea (18656.9 ind./km2, 383.4 kg/km2)r (P<0.05), which overlapped with the coastal upwelling area, and the density in August (after the seasonal moratorium on fishing) (mean 23727.4 ind./km2, 473.7 kg/km2) are significantly higher than that in November (mean 12299.6 ind./km2, 289.7 kg/km2) (P<0.001). The dominant species are small and low-value species such as Saurida undosquamis, Terapon theraps, Thamnaconus hypargyreus, Johnius grypotus, etc., and the composition of the dominant species varies among different waters in nearshore waters of Hainan Island. The similarity of the fish community in the southeastern waters in nearshore waters of Hainan Island is distinguished from the west, and the fish communities in the northern waters are characterized by the transition between the southeastern and western waters. Our study found that the fish communities in nearshore waters of Hainan Island has obvious spatial and temporal characteristics, and the decline and miniaturization trend of fish stock is still obvious. Therefore, it is suggested that the catchable resources and fishing intensity in different areas in nearshore waters of Hainan Island should be reasonably planned, with priority given to protecting the recruitment processes of fish resources and the integrity of habitats.