In this overall survey of the seagrasses of China 15 species are listed, eight of which are recorded for the first time. The Potamogetonaceae (subfamilies Zosteroideae and Cymodoceoideae) are represented by 10 species, and the Hydrocharitaceae (subfamilies Vallisnerioideae, Thalassioideae and Halophiloideae) by 5 species.Halophila ovalis (R. Br.) Hook. f. is represented by 2 subspecies. A key to the species based on vegetative and generative characteristics is presented.