Abstract: To reveal spatial and seasonal pattern of planktonic ciliate communities and its relationship with environmental variables, we investigated the planktonic ciliate composition, abundance and response to environmental changes during four seasons of 2014 in Dapeng Cove, the South China Sea. A total of 31 species belonging to eight orders were identified, 11 of which were dominant species. The average abundance of ciliate was 1 487 ind · L^-1 (10~5 040 ind · L^-1), and Tintinnida, Strombidium and Cyclotrichida were the most abundant in terms of number and abundance. Planktonic ciliate communities showed a distinct seasonal pattern of ciliate abundance and a clear seasonal shift of the taxonomic composition. The highest number of ciliate species occurred in summer, whereas the highest abundance peaked in spring, mainly due to the strombidium. Spatially, planktonic ciliate was more abundant and diverse in the cage fish culture area and oyster-algae mixed culture area, but the lowest abundance and species occurred in the estuary of Wangmu River. Multivariate analyses illustrate that ciliate abundance was significantly correlated with water temperature, nutrient level and chlorophyll-a concentration. Moreover, the dominant abiotic environmental factors affecting the seasonal pattern of ciliate communities were different between seasons.