Based on bottom trawl data from August 2006 to October 2007,seasonal variations in the fish community structure and diversity in the north of Liaodong Bay were analyzed using the index of relative importance(IRI),species diversity indices,and multivariate methods.A total of 39 species were collected,belonging to 8 orders,23 families,and 35 genera.Most of them were warm-temperature species and warm-water species.There were obvious succession of dominant species in four seasons,the seasonal dominant species whose IRI value ≧1000 were Chaeturichthys stigmatias,Synechogobius ommaturu,Larimichthys polyactis,Liza haematocheila,Platycephalus indicus,Protosalanx chinensis,Lophius litulon,and without symbiotic species in four seasons.Compared with the data in 1998,the dominant species have largely changed.The Margalef species richness index(D) ranged from 0.40 to 1.69,the Shannon-Winner diversity index(H') ranged from 0.39 to 1.45,the Pielou evenness index(J') ranged from 0.43 to 0.75,and all of three diversity indexes changed significantly among seasons(ANOVA).ANOSIM analysis also indicated that fish species composition varied significantly among seasons.The SIMPER analysis revealed that Larimichthys polyactis,Chaeturichthys stigmatias,Synechogobius ommaturus,Konosirus punctatus, Lophius litulon,Liza haematocheila,Platycephalus indicus,Scomberomorus niphonius,Pterogobius zacalles,Cynoglossus joyneri were primary discriminating species in the fish community among seasons.Based on the correlation between fish community structure and environmental factors using correlation analysis and BVSTEP,it is indicated that water temperature was primary environmental factor which led to seasonal changes of fish community in the north of Liaodong Bay.The study can provide a scientific basis for protecting ecological environment,fishery resources conservation and sustainable exploitation.