The experiments were carried out based on the competitive model of Lotka Volterra. The growth pattern of Scenedesmus obliquus (Turp.)Kütz. is different from that of Microcystis aeruginosa Kütz.. The amount of S. obliquus in mixed culture is larger than that in pure culture during the beginning growth stages; but is smaller during the later growth stages. The amount of M. aeruginosa in mixed culture is always smaller than that in pure culture in the whole growth duration. The competitive parameter(con...