Jiuduansha wetland is a typical shoal in Yangtze River estuary, which has a very important influence on fishery resources of Yangtze River and East China Sea. In order to comprehend community diversity and its variation trend, 16 surveys from 2009 to 2012 were made, and the results showed that(1)A total number of 12477 individuals were collected belonging to 96 species including 15 new records. (2) Combining with historical data, there were 158 fish species in Jiuduansha wetland, the Order Perciformes was at a dominant position, whose species were 54, the Order Cypriniformes ranked only second to the order Perciformes, comprising 27 species. (3)The dominant species were Acanthogobius hasta, Liza haematocheila, Liza carinatus, Coilia ectenes, Coilia mystus and Lateolabrax maculates. (4)Differences of fish?composition existed in Shangsha, Zhongsha and Xiasha, which revealed that salinity was a very import factor resulting of the difference in fish composition. This research showed that fishery resources of Jiuduansha wetland are abundant, and its fish composition has the typical ichthyofauna trait of Yangtze River estuary.But the diversity of fish species has declined year by year, and changes happened in its fish composition year by year.