Lake Ulungur is the second largest lake of Xinjiang Uigur Autonomous Region and one of the ten largest freshwater lakes in China.With the impact of human activities and climate variation, nutrients and biotic communities in the lake have been changed obviously.To understand the community of benthic macroinvertebrates and its response to the changes in their environ-ment, we surveyed the benthic macroinvertebrates community in Lake Ulungur seasonally from Nov.2006 to July 2008.In total, 87 taxa were recorded, including 61 Insecta (70.1%), 14 Oligochaeta (16.2%), 7 Mollusca (8.0%) and other 5 taxa (5.7%).The annual density and biomass averaged 1015.01 ind./m² and 9.83 g/m², respectively.The density was highest in winter(1234.96 ind./m²), followed by spring (1044.47 ind./m²) and autumn(931.16 ind./m²), and lowest in summer (849.44 ind./m²).The biomass of benthic macroinvertebrates was highest in winter(13.54 g/m²), followed by spring(12.01 g/m²) and autumn(8.37 g/m²), and lowest in summer(5.02 g/m²).The annual average value of Shannon-Wiener diversity index and Margalef diversity index was 2.19 and 1.34, respectively.Correlation analyses indicated that water depth was the key factor influ-encing the standing crops of the benthic macroinvertebrates in this lake.