Seasonal changes of number and biomass of zooperiphyton on suspended substrates in' Xuanwu Lake were studied. The main species are Epistylis plvcatdis,VoHicella convallaria, V orlicella campanula, Brachionus urceus and Brachionus cap suliflous. The number and the biomass of perihytic protozoan are large in summer and fall with their maximum number being 19952 ind. /cm² and the maximum biomass 296.6/ig/cm² in Station I, and with maximum number being 16393 ind. /cm² and the maximum biomass 246.5pg/cm² in Station II. The number of periphytic rotifera is large in fall and winter,with their maximum number being 873 ind. /cm² and the maximum biomass 958.3 ng/cm² in Station I in October and with their maximum number being 201 ind. /cm² and the maximum biomass 257 p.g/cm² in Station II in February. The yearly mean number for zooperiphyton is 4661 ind. /cm² and the yearly mean biomass is 391 /ig/cm² in Station I. The yearly mean biomass is 3037 ind. /cm² and the yearly mean biomass is 150.6jxg/cm² in Station II. So both the number and the biomass are larger in Station I than in Station II. According to indicative organism, the eutrophication has been very serious in Xuanwu Lake.