Abstract: The microstructure of the head-kidney and spleen of Oplegnathus fasciatus was observed using light microscope. The results showed that the surface of the head-kidney was covered with a very thin layer of fibroid connective tissue capsule but with no obvious trabcula; it was mainly composed of lymphoid tissue, blood vessels and sinuses; melanomacrophage centres were found. The surface of the spleen was also covered with a very thin layer of fibroid connective tissue capsule but with no obvious trabcula, mainly composed of lymphoid tissue (white pulp and red pulp), ellipsoid and melanomacrophage centres. The central artery and vein in the spleen usually moved together.