Abstract: In order to understand the fish composition and diversity of Guilong Mountain Nature Reserve in Fujian Province, and provide constructive suggestions for the management of nature reserve, a preliminary investigation of fish composition was carried out in July 2012, using Smith-Root electrofisher(LR-24). Nineteen fish species, which were collected from 6 sites, were belonging to 5 orders, 8 families and 16 genera. The largest group of the fish community was from Cypriniformes, representing the typical fauna characteristic of oriental realm. Most species were omnivorous fishes living in the benthic zone of the mountain streams. The community diversity at each site was measured using the Shannon-Weiner index, Pielou evenness index, richness index and similarity analysis. The results showed that community diversity varied among sites. The analysis of relative importance index demonstrated that Zacco platypus, Distoechodon tumirostris and Acrossocheilus parallens were the dominant species among all sampling sites.