From Apr 1997 to Mar 1998, using the qualitative and quantitative methode, a study on the ecology of planktonic ciliates in an urban lake in Guangzhou-Yuexiu Lakt, was carried out In the study, some param eters of the ciliate community lice species compositibn abundance biomass and biodiversityind ices were analyzed 76 ciliate species were recorded The results showed that themajy dominant species were Halteria grandinella Strobilndium caudatmn, Strobilidium humile Cyclidium spp and U rotricha spp., the maximum total abundance was 6 91×10⁴ ind °L^-1 in May, meanwhile, the maxmum totalbiom ass was 7.16mg°L^-1 in June The population dynamics and succession of dominant species were studied aswell Based upon the structuralparam eters of the ciliate community, a comparison with literatures the water quality of the lake can be considered beiig hypereu trophic.