Abstract: According to the survey data of gill net and hand fishing in Zhubi Reef of Nansha Islands in 1999−2018, we analyzed Zhubi Reef fish species composition and the classification of diversity, calculated the average classification difference index (Δ⁺) and classification difference variation index (Λ⁺). Altogether 152 species of reef fish belonging to 11 Orders, 43 Families and 93 Genera had been found. Among them, Perciformes fish accounted for an absolute advantage (76%). The Δ⁺ and Λ⁺of Zhubi Reef fish were 58.75 and 102.60, respectively. Compared with the composition of fish communities in different ecosystems at home and abroad, the Δ⁺of the fish in Zhubi Reef was higher than those in Zhaoshu Island, Milne Bay and San Jose Island, but lower than those in the East China Sea Shelf, the South China Shelf of Nansha Islands, Beibu Gulf and Daya Bay. The Λ⁺ of the fish in Zhubi Reef was lower than those in the other islands. It is indicated that the genetic relationship among the species in Zhuubi Reef fish community is closer than those in the East China Sea Shelf, the southwest shelf of Nansha Islands, Beibu Gulf and Daya Bay, but farther than those in Zhaoshu Island, Milne Bay and San Jose Island. The fish diversity of Zhubi Reef is characterized by higher species diversity but lower taxonomic diversity. However, the reef is vulnerable to human activities and should be protected in a timely manner.