The species composition and distributional patterns in marine benthic algae at intertidal zone in Masan Bay were investigated seasonally throughout 2007. A total of 42 species, 5 Chlorophyta 8 Phaeophyta, and 29 Rhodophyta were recorded, and dominant species were Enteromorpha linza, Ulva pertusa, Sargassum thunbergii, Gelidium amansii, G. divaricatum, Corallina pilulifera, Gracilaria textorii, and Polysiphonia morrowii during study periods. Especially the vertical distribution of dominant algal species was remarkable : U. pertusa and G. divaricatum were dominated in the upper part, E. intestinalis, E. linza, S. thunbergii and G. divaricatum were in the middle part, and U. pertusa, Undaria pinnatifida, S. thunbergii, G. amansii, G. divaricatum and C. pilulifera mainly occurred in the low part of tidal zone. The numbers of species were different with seasons and stations; Higher number of species was 38 species in winter, whereas 28 species were the lowest in fall. The number of species was higher at stations 4 and 6 while the lower value was at stations 1 and 2 than other stations. The spatial distribution of marine benthic algal composition in dendrogram and MDS ordination was due to differences in the local topography and physical characteristics such as current and water movement.