In order to investigate the polarized light scattering between films and substrates, first-order vector diffraction theory is applied to derive the polarized bidirectional reflectance distribution function (PBRDF) of substrate. The analysis results are compared with the experimental ones, and the influence of the thickness of SiO2 and TiO2 films on the PBRDF is numarically simulated, at interfaces roughness perfectly correlated and completely uncorrelated models, respectively. And the relation between dielectric constant and the PBRDF is discussed. The results show that with the increment of thickness of SiO2 films the PBRDF is coincident little by little at interfaces roughness perfectly correlated and completely uncorrelated models. And film can perfectly replicate surface profile of substrate at this time. With the increment of thickness of TiO2 films, the PBRDF becomes larger and larger, which illustrates that TiO2 film has smoothing effect on the roughness of the substrate. The real part and imaginary part of dielectric constant have opposite influences on the PBRDF. The optical information of the substrate can be measured and calculated by the PBRDF of different films.