Abstract: We investigated the composition, diversity, and structural characteristics of fish resources in summer in Daya Bay, South China Sea, based on data collected from one otter trawl survey in August 2018. The results showed that 56 species were collected in 2018, belonging to 47 genera, 34 families, and 9 orders. Among them, species of Perciformes (39 species) were predominant, accounting for 69.64% of the total species richness. Dominant species included Leiognathus brevirostris, Siganus oramin, Parachaeturichthys polynema,Polynemus sextarius, and Evynnis cardinali, which are lowvalue fish with small stature. There was significant spatial variation in fish species diversity, with the greatest value in the mouth area, followed by that of the coastal waters, and the lowest in the central area. The fish community structure could be roughly divided into two groups: bay type with brackish water and bay mouth type with seawater. Compared with the summer survey data of 1985-2017, fish species diversity in the Daya Bay had been decreased over the past 30 years. The compositions of dominant fish species had been changed significantly, from large-stature pelagic economic fish to small-stature and low-value fish in bottom and near-bottom layer. The main reason for such changes was anthropogenic disturbance, especially the fishing activities, which led to simpler fish community structure.