In the present paper, 10 species and 2 forms of the crustose coralline algae from the Hainan and Naozhou Islands，Guangdong Province, are reported together with a study of their morphology. The specimens used for this study were collected by the members of the Institute of Oceanology, Academia Sinica during 1957-1965, 1973-1976, 1980-1982, and by Prof, C. K. Tseng in 1933-1934. Among them, Mastophora rosea (C. Ag.) Setch. (or as Mastophora macrocarpa Mont.) was already recorded from Hainan I. and Dongsha Is. of Guangdong Provincer[44] and Taiwan Province [8]; the other four species and 2 forms, i.e., Mesophyllum erubescens (Fosl.) Lemoine, Mesophyilum simulans (Fosl.) Lemoine f. typica (Fosl.) Lemoine, M. simulans (Fosl.) Lemoine f. crispescens (Fosl.) Lemoine, Lithophyllum kotschyanum (Unger) Fosl. and Lithophyllum moluccense Fosl. were briefly described for the first time in Common Seaweeds of China[49] recently by the present authors; Hydrolithon reinboldii (W. v. Bosse et Fosl.) Fosl., Lithoporella melobesioides Fosl., Lithoporella pacifica (Heydr.) Fosl. and Porolithon onkodes (Heydr.) Fosl. are compared with the related species from the Xisha Is.The last one, living form of Archaeolithothamnium erythraeum (Rothpl.) Fosl. [ = Sporolithon erythraeum (Rothpl.) Kylin] found in the Hainan I. is new to China, and most of its sporangia are cruciate and some zonate, they are arranged in rather loose sori and generally in several layers. The “ cover cells" characterized by all the members of both genera，Archaeolithothamnium and Lithothamnium, are clearly present in the Hainan specimens of Archaeolithothamnium erythraeum. The argument has long existed among some phycologists on the generic name, Archaeolithothamnium or Sporolithon. In China, 4 fossil species of the genus Archaeolithothamnium had already been found among the late Cretaceous and the early Tertiary calcareous algae distributed in the Qomolangma district of the Himalayas[1], and now, its living species, A. erythraeum, was also collected from the Hainan l. We think it is rather reassonable and logical to use a common generic name for all members of a common genus whether they are fossils or living forms, and not that Archaeolithothamnium only for the fossils while Sporolithon for the livings.