Abstract: This article reports the morphology, densit ies and distribution characteristic of 13 dinoflagellate resting cysts in sediment of Xiamen Harbor. The preliminary study showed that the average abundance of dinof lagellate cysts is 3360 ind..kg - 1 ( wet sediment ) . Among them 2 species are toxic ( Alexandrium tamarenes, A. minutum) and 2 species are harmful ( Gonyaulax spinif era, Scripp siella trochoide) . These 4 toxic and harmful dinof lagellate cysts are rich in the sediments of Xiamen Harbor. They will be harmful to the aquaculture in Xiamen Harbor and human health when the environmental factors are appropriate.