Abstract: According to the beam trawl surveys in Jiulong River Estuary in autumn of 2015, this paper studied and analyzed the species composition, distribution characteristics and the diversity of nekton. The results showed that 61 species were identified, including 42 fishes, 8 crabs, 6 shrimps, 3 stomatopodas and 2 cephalopods. The average density of its resource was 518 ind/h and 10.29 kg/h, the dominant species in catch were Coilia mystus, Parapenaeopsis hardwickii, Charybdis japonica and Solenocera crassicornis etc. The species richness index (D) varied between 3.112 and 4.682, the average was 3.921;the Shannon-wiener diversity index (H') varied between 1.814 and 2.674, the average was 2.390;the species evenness index (J') varied between 0.606 and 0.921, the average was 0.789;the diversity index was at moderate level.