Abstract: Phosphorus in water of lake Donghu, Wuhan was fractionated into five sorts of P fractions;total soluble phosphorus(TSP), soluble reaction phosphorus(SRP), total reaction phosphorus(TRP), soluble hydrolysable phosphorus(SHP)and particular phosphorus(PP). Effects of these P fractions on the growth of Chlorella vulgaris were investigated. The regression equations between each P fractions as well as total phosphorus(TP)and the growth of Chlorella vuigaris were obtained and compared with each other. The models of growth of Chlorella vulgaris(N)depending on P fractions were established by multiple regressing, and three models can be helpful for predicting the potential growth of the algal and assessing the eutrophication of the lake.