Abstract: An investigation was made on the abundance and biomass of planktonic ciliates in the shelf of East China Sea in May (spring) and November (autumn), 2011. The abundance of the ciliates in spring and autumn was averagely (614±861) and (934±809) ind·L^-1, and the biomass was averagely (1.70±3.91) and (0.93±0.99) μg C·L^-1, respectively. The high abundance and biomass in spring were found in coastal and offshore areas, and those in autumn were in offshore only. In the two seasons, the ciliates tended to accumulate in the waters upper layer, and sometimes flocked in the bottom. In the spring, aloricate ciliate species were larger than those in the autumn. Tintinnids occupied (26.9%±34.3)% and (44.9%±25.2)% of the total ciliates abundance in spring and autumn, respectively. In taxonomy, 52 tintinnid species of 27 genera were identified. The most dominant species were Tintinnidium primitivum, Stenosemella oliva, and Tintinnopsis tubulosoides in spring, and Tintinnidium primitivum, Stenosemella parvicollis, and Tintinnopsis nana in autumn. The ciliates abundance showed significant positive correlations with water temperature and Chl a concentration, the tintinnids abundance showed significant negative correlation with water salinity, and the tintinnids community was significantly related to water temperature.