Abstract: Community structure and species diversity of metazoan zooplankton was investigated monthly from May 2009 to March 2010 in Gehu Lake. A total of one hundred species of metazoan zooplankton were found and identified as 52 species of Rotifera under 25 genera, 21species of Cladocera under 12 genera, and 27 species of Copepoda under 14 genera. The community was dominated mainly by Brachionus calyciflorus, Brachionus angularis, Polyarthra trigla, copepodid and Bosmina longirostris, with rotifera accounting for 98.7% of the total.The density of the zooplankton was 1 572 L^-1 on average annually and peaked in spring, while the biomass of the  zooplankton was 2.34 mg•L^-1 on average annually and peaked in summer. The biomass of Cladocera was significantly and positively related to the density of Copepoda ( r = 0.516，P＜0.01) , whereas the biomass of Rotifera negatively related to the biomass of Copepoda. Density and biomass of the metazoan zooplankton varied sharply with the season, showing an descending order of spring ,summer,autumn,and winter,and of summer,spring,autumn,and winter, respectively. The values of the Shannon-Wiener diversity index，Margalef species richness index and Pielou index indicate that the Gehu Lake was light to moderate in pollution.

Key words: Gehu Lake, metazoan zooplankton, community structure, species diversity