The present paper deals with descriptions of 11 species of marine blue-green algae belonging to 5 orders, 6 families and 10 genera from the Xisha Islands, Guangdong Province,China. With the exception of 5 species, i.e., Hyella caespitosa Bornet et Flahault, Phormidium fragile Gomont, p.corium Gomont, Mastigocoleus testarum Lagerheim and Kyrtuthix maculans (Gomont) Umezaki reported from Guangdong and Shandong Provinces, the other 6 species, i.e.,Synechocystis aquatilis Sauvageau, Dermocarpa solitaria Collins et Hervey,Dalmatella buarnsis Ercegovic, Trichodesmium hildebriandii Gomont, Lyngbya adherens Setchell et Gardner and Sirocoleum kurzii (Zeller) Gomont are new records for the Chinese marine blue-green algal flora. These specimens studied were collected from the Xisha Islands during 1975 and 1976,and are deposited in the harbarium of the Istitute of Oceanology, Academia Sinica, at Qingdao (Tsingdao).