Species composition of aquatic organism in the marine ranching area of Gunsan, Korea were investigated using shrimp beam trawl from May to December in 2010. A total of 91 species, 98,127 ind./ and 877.6 / of aquatic organism were collected. Among them, species were included 60 species in ㎢ ㎏ ㎢ Pisces, 21 in Crustacea and 10 in Mollusca. The individual dominant species, occupying over 10% of total individuals, were Latreutes anoplonyx(47,327 ind/ , 48.23%), ㎢ Crangon hakodatei(11,578 ind./ , 11.80%) ㎢ and Trachysalambria curvirostris(10,237 ind./ , 10.40%). And the biomass dominant species, occupying ㎢ over 9% of total biomass, were Paralichthys olivaceus(135 / , 15.4%), ㎏ ㎢ Okamejei kenojei(98.2 / , ㎏ ㎢ 11.2%) and Portunus tribuberculatus(84.8/ , 9.6%). From the cluster and MDS analysis based on ㎏ ㎢ Bray-Curtis similarity matrix of fourth root transformed data of number of species and individuals per unit area collected more than two times during this survey by each month and station was divided into three different groups. Group A showed seasonal similarity of characteristic of distribution in August and November, Group B in December and Group C in May.