Abstract: The annual dynamics of rotifer community structrue in Lake Jinghu in Wuhu city in 2003 was studied and the water quality was ecologically assessed.The relationships between the rotifer density and the main ecological factors including water temperature,pH,and the densities of small Ciliates,Cladocera and Copepoda were also regressively analyzed.55 species of rotifers were identified,which belong to 15 families and 21 genera.The dominant species determined according to annual average denstity and biomass included Anuraeopsis fissa,Trichocerca pusilla,Rhinoglena frontalis,Polyarthra remata,Filinia longiseta,Polyarthra vulgaris,Proalides tentaculates,Asplanchna priodonta,Proalides tentaculates and Trichocerca pusilla.The total density of rotifer was positively correlated with water temperature (w),Chl2a concentration (c) and small Ciliates density(x) (multiple-linear regression,R2=0.38 P< 0.05),and water temperature had the greatest effect on the total density of rotifers (Standard partial regression index,βw =0.684,βc=-0.246,βx=0.422).In spring and winter,Chl-a concentration had the greatest effect on the total density of rotifers(βw1=0.983,βc1=-0.683;βc2=-0.631,βx2=0.566).But the total density of rotifers was not positively associated with neither the small Ciliates density or the water temperature.While in summer and autumn, the density of Ciliates and water temperature had the greatest effect on the total density of rotifers,respectively(βw1=- 0.225,βc1=-0.154,βx1=0.871;βw2=0.642,βc2=0.423,βx2=-0.583).By means of three biological standards(QB/T,Shannon-weiner diversity index and Willams index,indicator organisms of rotifer species)combined with Physico-Chemical quality of water,the small region of Lake Jinghu(Station Ⅰ)could be regarded as transition stage from oligo2βmesosaprobity toβmesosaprobity,while the big region(Station Ⅱ) could be considered asβmesosaprobity.The lake might be a meso- eutrophic lake.Although some methods including removing the bottom mud,intercepting the polluted water flowing into the lake and the water exchange have been taken,the improvement of the water quality in Lake Jinghu was not significant.It is necessary to adopt more methods including the bio2manipulation to restore Lake Jinghu"as clear as a mirror".