Abstract: Seasonal changes and horizontal distribution of zooplankton community structure and diversity were investigated in the lower branch of River Wusuli in spring（May）,summer（July） and autumn（October） of 2010.The results showed that the zooplankton population was heavily comprised of Protozoa（abundance of 87.8 %）,and Rotifera（biomass of 68.4 %） in which there were small dominant species in size and higher diversity,supplying abundant natural food resources for many excellent native aquatic animals,especially for Pacific salmon Oncorhynchus keta Walbaum in the lower branch of River Wusuli where was the important reproductive and growth grounds of the excellent native aquatic animals in China.The abundant zooplankton featuring active metabolism,rapid reproduction,and wide distribution had a great role in material circulation and energy flow because it was the important part of aquatic ecological system in River Wusuli.Also,the zooplankton was characterized by sensitive reflection to changes in water quality,and then was widely used in river health assessment.

Key words: lower branch of River Wusuli, zooplankton, community structure, river health assessment