To investigate the composition and biomass of fish community in the middle and downstream area of Ganjiang River,10 points from Xiajiang to Nanchang section at high-water period,normal-water period and low-water period were sampled from June 2009 to June 2010.A total of 90 species of fish,which belonged to 60 genera,16 families and 6 orders were recorded.The results showed that Cypriniformes were the major fish species,Siluriformes and Perciformes were the next and the Clupeiformes,Synbranchiformes and Beloniformes were the least.The dominant species in the present study were Cyprinus carpio Linnaeus,Carassiu auratus (Linnaeus) and Pelteobagrus fulvidraco (Bleeker).The population of migration fish including Mylopharyngodon piceus,Ctenopharyngodon idellus,Hypophthalm ichthys molitrix,Aristichthys nobilis,etc decreased sharply.The species of the Acipenser sinensis,Luciobrama macrocephalalus,and Hilsa reevesi disappeared completely.Compared with the historic data,the composition of fish species from Xiajiang to Nanchang section in Ganjiang River varied dramatically,the resource of fish decreased obviously and the fish became smaller.