A survey of rotifers was carried out at four sites in a reservoir in Guangdong Province, from August 2006 to August 2007. Turbidity, Chlorophyll a (Chl a), Total Nitrogen (TN), Total Phosphorus (TP) were measured. Forty-one species of rotifers were recorded during the survey. The dominant species were Polyarthra vulgaris and Synchaeta stylata. The rotifer densities ranged from 6 to 1966 ind./L. There was a significant positive correlation between rotifer densities and chlorophyll a concentrations. Canonical correspondence analysis (CCA) was applied to explore the relationship between rotifer species and environmental parameters. The result of CCA showed that turbidity, transparency, temperature and chlorophyll a concentration were the most important factors regulating the composition and temporal-spatial dynamics of the rotifers community. Trophic state indexes (TLI) based on data of TN, TP, CODMN and chlorophyll a concentration ranged from 30 to 40, indicated the reservoir was in the meso-trophic level.