Macroinvertebrate was seasonally sampled at 14 sites of four regions(Regions Danjiang, Hanjiang, Wuqing, and thewater intake) of the Danjiangkou Reservoir from July 2007 May 2008. In total, 61 taxa were collected, mainly including Oli-gochaeta (Tubificidae and Naididae)and Chironomidae. Oligochaeta was dominant in the density of the macroinvertebrate allthrough the year, with the relative abundance over 90.The dominant species of the hiomass was, however, the Annelids. In thespatial distribution, the highest density appeared in Hanjiang region m²),and then in the Dan-jiang region. The densities in the water intake region and the Wuqing region were relatively low. For the hiomass, ii was relativelyhigh in Danjiang and the water intake regions, for the appearance of some Annelids species. Seasonally, the density was highest insummer, and then higher in spring, autumn and winter. The trend of the biomass distribution was similar in seasons, with littledifference between autumn and winter.Water quality was estimated by multiple methods of Shannon-Wiener diversity, Goodnight-Whitley index, Wright index and the Carlander's biomass.fy comparing all the assessment results, we could conclude that, Good-ni t-Whilley index was nut appropriate for the assessment of the water in Danjiangkou Reservoir. The assessment results by combi-sing other three methods showed that, the pollution extent was weak in water intake region, intermediate in Danjiang region, inter-strong in Hanjiang region. For Wuqing region, it was not suitable to be estimated by ma roinvertehrate, due to the shallow water depth and various macroinvetebrate community structures sensitively impacted by the water conditions.