Abstract: The function of UV-B radiation on growth and pigments biosynthesis of three strains of Microcystis Aeruginosa (FACHB 469,854 and 905) was studied.The results indicated that the UV-B radiation decreased the reproductive rate of M.aeruginosa and increased intracellular and extracellular polysaccharide biosynthesis.There were different adaptabilities to UV-B among the three strains of M.aeruginosa.