The over-increasing of nitrogen and phosphorus as well as algae is the main indexes of eutrophication, in which phosphorus is the key factor of eutrophication in most lakes. Studies indicated that various algae in eutrophic water bodies depend on the different content of phosphorus. The effect of various phosphorus concentration on growth rate of chlorella, diatoms and natural algae under the same condition of nitrogen concentration and temperature was analysed, and results showed that high concentration of phosphorus improved the growth of chlorella when nitrogen content was sufficient but has no obvious correlation to the growth of diatoms, and phosphorus concentration has positive correlation to the growth rate of natural algae.