Abstract: Gills were operated with scanning electron microscopy (SEM) in Epinephelus fario (Thunberg) and Siniperca kneri Garman，both of which belong to Serranidae,Perciformes,and benthic living and ferocious predatory fishes.The results indicate that the surface architecture and ultrastructure of gill of two species of fishes are similar to other teleosts.They show the presence of various features such as regular and irregular circular microridges,indentations,micropits and crevices.However,their secondary gill lamellaes are rather higher and their surfaces much more concave and unevenness.It maybe acclimates to lower dissolve oxygen in the bottom of water.Some surface architecture of gill filaments of Efario are smoothness,the others are concave and unevenness.The height of secondary gill lamellaes of E.fario is higher than that of S.kneri,so the formers surface area is larger and respiratory efficiency better than the latters. Three kinds of epithelial gill cells,I.e. pavement cell,chloride cell and mucous cell in E.fario and S.kneri can be distinguished under SEM:The limit of pavement cells in the former is well defined by long and circular microridges,but in the latter characterized by irregular microridge throughout the cell surface,with unclear definition of cell boundaries;The number of chloride cells of the gill filament and lamellar in the former is higher than in the latter,and the morphology of chloride cells of both fishes are different;The number of mucous cells of the gill in the former is lower than in the latter.Those differences may be related to inhabit environment and mode of life of two species.The former live in seawater,while the latter live in fresh water.