Abstract: Two high yield gentamicin strains of Micromonospora purpurea were screened by agar plate or/and liquid medium composed of high concentration of gentamicin after implanted by suitable doses of N+ at 30 KeV and exposed by UV.The yields of these two strains were 75.1% and 70.2% higher than that of the original strain,respectively.And the gentamicin C component is qualified to the Medicine Code of China 2000.