The seasonal variations of the marine algal community were detected with quadrat method during May, 1974-May, 1975 at several stations in the Kwang Yang Bay. Considering the environmental factors such as salinity and water current, etc., and algal vegetation, the Bay was divided into 3 sections; Section I-Myodo and the adjacent area; SectionⅡ-Eomnamuseom and the adjacent area; SectionⅢ-inlet of the Bay from Odongdo, Yeosu. The dominant species, shown by 5-grades coverage and bimonthly investigations, appear in the order of Sargassum thunbergii(Jan.)>Chondria crassicaulis(Mar.)>Ulva pertusa(May)>U. pertusa(July)>U. pertusa and Gigartina intermedia(Sept.)>Sarg. thunbergii and Gelidium pusillum (Nov.) in Section I, and Sargassum thunbergii(Jan.)>Ulva pertusa and Hizikia fusiforme(Mar.)>U. pertusa and Sarg, thunbergii(May)>Chondria crassicaulis(Sept.)>Ch. crassicaulis(Nov.) in SectionⅡ. The members such as Sargassum thunbergii, Gelidium pusillum, G. divaricatum, Hizikia fusiforme, Carpopeltis affinis, and Chondria crassicaulis show the most luxuriant period of growth in winter(Nov.-Mar.), while Ulva pertusa shows the period in May. However, considering the dry weight of total vegetation, the most luxuriant period appears in May and the poorest one in July. The total dry weight of the vegetation in Section Ⅱ is about 3.2 times more than the one in Section Ⅰ.