This study deals with the growth characters and pure culture of Microcystis from Taihu Lake. It is found that Microcystis flos-aquae can grow in solid medium. The results also show that both phosphorus and nitrogen play an important role during the growth period of Microcystis flos-aquae. The maximum growth rates appear when the PO₄^3- concentration reach 1.7 mg·L^-1 and the TDN concentration reached 17 mg·L^-1. Comparing the indoor culture of Microcystis with the Microcystis in the lake, there is a clear difference in their growth characters. The Microcystis in the lake normally appears as big colony while it appears only single cell or small colony with ten cells in indoor culture.