Mathematical model to calculate the Bidirectional Reflectance Distribution Function(BRDF)of laser scattering from rough surface was established based on small slope approximation.The model was used to calculate BRDF of alloy aluminum with given roughness.Theoretical data and experimental data were found in good agreement,which verifies the correctness of the model.Further study of the effects of roughness and sample optical parameters on bidirectional reflectance distribution function was carried out.Results show that the BRDF of laser scattering is related to root mean square height,correlation length of rough surface and optical parameters of the sample.As the incident wavelength is fixed,the diffuse reflectance of incident laser is stronger when the RMS height is greater,or when the correlation length is smaller,and the value of BRDF is more dispersed with smaller peak.As the surface roughness is fixed,the optical parameters of the sample have great influence on the value of BRDF.The peak value of BRDF is smaller while the imaginary part of refractive index is larger.With the increment of roughness,the effects of optical parameters on BRDF decrease gradually.