AbstractDuring May to July 2004 and March to April 2005, we carried out two cruise surveys on fish resources using trammel net in the adjacent waters of 23 coral reefs of the South China Sea. We analyzed fish species composition and community characteristics. The results showed that Carcharhiniformes and Myliobatiformes were dominant families of the cartilaginous fishes, while Perciformes and Teraodontiformes were dominant families in the bony fishes. We defined the species with an Index of Relative Importance (IRI) >500 as dominant species. Accordingly, five dominant species were found in Xisha Archipelago waters, namely Taeniura meyeni, Lethrinus miniatus, Plectorhinchus pictus, P. flavomaculatus, and Hexanchus griseus. Six dominant species were found in the Zhongsha Archipelago water, namely Plectorhinchus flavomaculatus, Taeniura meyeni, Platax orbicularis, Dioson hystrix, Lethrinus rubrioperculatus, and Plectorhinchus pictus, and the three dominant species were in the Nansha Archipelago water, Carcharhinus limbatus, Triaenodon obesus, and Caranx stellatus. Since the fish body sizes varied remarkably, we calculated Margalef richness index, Shannon-Wiener index, Simpson index and Pielou evenness index based on both individual number and biomass. The results indicated that fish species diversity in coral reefs water were significantly different compared with those either in the northern or southwestern continental shelf waters of South China Sea. Fish species in similar habitats had higher similarity.