Abstract: The spatial and temporal distributionof planktonic rotifers in the Guangzhou segment of the River Pearl,China, was investigated at half of month intervals from April 2004 to April 2005. Samples were taken at two fixed sites(Zhong da port andHuangpu harbour). 65 species of rotifer belonging to 20 genera and 13 families were identified during the survey period. Filinia Novaezealandiae and Lecane elegans were confirmed as new records in China. The dominant species were Anuraeopsis fissa, Brachionus angularis, Brachionus caudatus, Filinia novaezealandiae, Trichocerca pusilla and Liliferotrocha subtilis. Results indicated that river discharge had important effect on the density fluctuation of rotifers. The highest densities were recorded in the beginning of summer and the end of autumn. The lowest densities were in the rainy season (flood period) and the late dry season (low water period), respectively. The importance of salinity and temperature in determining rotifer community structure and seasonal succession are analyzed. Results indicated that rotifers played an important role in river ecosystems.