Based on data of surveys by beam trawler in the East China Sea,the occurrence frequency,species composition and dominant species,and resource density of flatfishes were analyzed.A total of 71130 flatfish specimens were caught and weighted 4.92% in the total catch.Fifty-one species were identified in 26 genera of 7 families,most in Cynoglossidae and Bothidae.The occurrence frequency of flatfishes was 95.91%,and the most frequently caught species were Cynoglossus joyneri and Pleuronichthys cornutus.The dominant species were C.joyneri and Pseudorhombus cinnamoneus by the index of relative importance (IRI).