The radiative properties of a gold surface with one-dimensional Gaussian random roughness distribution were obtained with the finite-difference time-domain (FDTD) method and the recursive convolution treatment of the Drude Model.The bi-directional reflection distribution function (BRDF) for both TM mode and TE mode were obtained and compared with the highly accurate experimental data from the earlier work.The incident wavelength varies from 1.152 μm to 3.392 μm and incident angle is at 30°-70°,respectively.The results show that,the predicted values and experimental results are in good agreement.The highly specular peak in the BRDF is reproduced in the numerical simulations,and the increase of the TM mode BRDF is found to be attributed to the effect of a variation in the optical constant at the incident wavelength period.