In order to study the changing rule of single layer thin film surface roughness using light scattering, the polarized bidirectional reflectance distribution function(P-BRDF) of the single titanium dioxide thin film at fully correlated and uncorrelated model were researched respectively based on the vector scattering theory of optical thin film. The relationship of scattering azimuth angle and BRDFpp, P-polarized scattered light caused by P-polarized incident light, was researched. The theoretical results show that BRDFpp strongly depends on the correlation between interfaces roughness of thin film and substrate with azimuth angle changing. The scattering azimuth angle of BRDFpp valley value can decrease with the increase of incident angle at fully correlated model. The result is reverse to uncorrelated model. BRDFpp does not appear valley value as the change of scattering azimuth angle.