Our recent investigations have shown that the Xisha Islands (Guangdong Province, China ) have a rich cyanophyceous flora. The present paper deals with descriptions of 10 species of marine blue-green algae belonging to 3 families and 6 genus of Chroococcales. With the exception of Chroococcus turgidus (Kuetzing) Naegeli and Entophysalis granulosa Kuetzing, respectively reported from Fujian and Shandong Provinces, the other 8 species, namely, Microcystis aeruginosa Kuetzing, Chrococcus minor (Kuetzing) Naegeli, C. limnticus Lemm. var subsalsus Lemm. C. varius A. Braun, C. membraninus (Meneghini) Naegeli, Gomphosphaeria aponina Kuetzing, Hormathonema epilithicum Ercegovic and Joannesbaptistia pellucida (Dickie)W. R. Taylor et Drouet ate recorded for the Chinese marine flora for the first time. During the last century, according to most of the current systems of classification of the Cyanophyta, the chroococcaleous algae were generally divided into 2 families, namely, Chroococcaceae and Entophysalidaceae. Until 1963, G. Claus proposed to retain the Tubiellaceae in the Chroococcales as one of its families. We agree with G. Claus’s point of view, to divide the Chroococcales into 3 families: Chroococcaceae, Entophysalidaceae and Tubiellaceae. The specimens of Johamnesbaptistia were collected from Zhongjian Island of the Xish Islands,in February 1976. The present specimens are closely resemblance to those specimens described by Drouet (1936 ) in shape and size. All of specimens studied are deposited in the Herbarium of Institute of Oceanology, Academia Sinica at Qingdao.