This paper reports morphological study on Ditylum sol by light (LM) and scanning electron microscopes (SEM). The cell of D. sol is prism shaped.LM showed the valve of D. sol is triangled and with fine puntae in radial rows. The middle part of the valve margin is concave. A strongly hollow spine appears at the valve center. SEM showed radially arranged rota (elongated, 0.8-5μm in length), and scattered open-pores on the valve face and a labiate process at the inside of the valve.On the valve mantle are some small rotas (04-0.8μm in length) arranged in parallel. Numerous small pores distribute on the connecting band of this species. Some diatomists stated that the valve of the species of genus Ditylum (including D. so1) is composed of interior and outer triangled, portion as they mistook the valve mantle for the outer triangle.