The aim of this paper is to study swimming animal composition, dominant species, diversity, niche and community structure in Qixing Islands offshore area, according to taxonomy of ocean swimming animal, IRI formula, Primer, Excel, niche, ABC curve for swimming animal identification and data processing and analysis. The results showed that there are 80 swimming animal species belonging to 3 classes and 14 orders living in the investigated area, including 52 fishes, 13 shrimps, 10 crabs and 5 cephalopods, by the bottom trawl catches in autumn of 2014 and spring of 2015. There were 6 dominant species in autumn, and in spring the dominant species were 4. One common species is Portunus trituberculatus. In the two quarters, the species diversity index H', D, J' was at the middle level. The species of larger niche in the autumn was Polynemus sextarius (10.51), Parapenaeopsis harbwickii (9.47), Muraenesox cinereus (8.84) etc and in the spring was Loligobeka (8.93), Oratosquilla oratoria (8.51), Trichiurus lepturus (7.94) etc. Cluster analysis showed the species among 12 stations of two seasons can be divided into three groups.The result was consistent with the NMDS analysis. The ABC curve analysis showed that the W vaule was 0.052 in the autumn and -0.059 in the spring which were close to zero. The swimming animal community composition was based on fish, followed by shrimp and cephalopods at last. P. harbwickii, M. cinereus and O. oratoria etc., the low value nekon has the high niche and occupied a major competitive position.In the two quarters, the grouping of the species among 12 stations was not affected by the season, because the composition of species and marine environment had a certain degree of similarity in the group of stations. ABC curve analysis showed that the offshore area was in a state of intermediate interference.