Abstract: Scattering of optical mirror surface makes a very important impact on properties of optical system. Laser transmission characteristics with different pollution conditions on optical mirror surface had been researched by using modified Mie theory and Bidirectional Reflectance Distribution Function(BRDF) of optical mirror surface, under three laser wavelengths of the visible light 0.632 8 m, near infrared light 1.053 m and thermal infrared light 10.6 m. The results show that if mirror surface roughness is much smaller than the incident wavelength ( ), scattering magnitude of clean mirror surface is proportional to and inversely proportional to . Scattering magnitude of particulate-contaminated mirror surface relates to size and quantities of particles on the mirror surface. The more complex particles distribute, the more significant scattering will be. In addition, when wavelength is shorter, BRDF will be greater, and scattering becomes very complicated.