Abstract:The species and distribution of the cysts of dinonagellates and other organisms inDapeng Bay, the South China Sea, was investigated in March 1992 at 12 sites bycollecting the sediments on sea-bed. From cysts of 30 species found, Scrippsiella trochoideawas the most dominant one at all sites investigated, and Gonyaulax polyedra, Protoperidiniumavellana and Alexandrium tamarense were common species. It was found that highest cystabundance was in sediment at site under deep water and in sediment at site where waterflow was stable. Most of the living cysts accumulated in sediment layer at 0-5 cmwith high phospate concentration and low N/P value. On the basis of the distributionof cysts of different species, the possible outbreak of red tide is disccussed.