Abstract: In base of the data of the trawl surveys from 2006 to 2007, we investigate the species composition and diversity of fishes in the coastal waters of Hainan Island. The results show that the area is rich in fishes with 292 species collected, belonging to 21 orders, 100 families and 172 genera. Warm-water and warm-temperate species account for 83.32% and 16.78% of the total number of species, respectively. Mutual species in the coastal waters of Hainan Island with the Yellow-Bohai Sea and East China Sea are 76 and 220, respecitively; those with the continental shelf, continental slope and waters around islands in South China Sea are 279, 42 and 51, respectively. The dominant fish species with IRI index 500 are: Acropoma japonicum, Apogonichthys carinatus, Leiognathus bindus, Johnius belengeri, Argyrosomus macrocephalus, Therapon theraps, Gastrophysus spadiceus and Bregmaceros macclellandi. Five indices of species diversity based on biomass are used for analysis, and seasonal dynamics of replacement index and migratory index are also applied to assess the stability of fish community. Results indicate that the fish diversity is high in the waters; the fish species in adjacent seasons are similar, and the community becomes unstable because of seasonal migration of fish.