Abstract: The synergistic effects of pH value, ratio of N/P, and light limitation on the growth ofMicrocystis aeruginosa were investigated by orthogonal tests. Results of orthogonal test for the selective preference of the growth condition for M.aeruginosa showed that pH can significantly affect the growth of M.aeruginosa, and the optimal factor combination is pH 10.5, stress of 5 days and 15/1 for N/P. Under 25 ℃, the order of effect on the M.aeruginosa is pH> stress of light limitation > N/P, detected after cultured under normal light intensity for 4 days.