The complex refractive index of materials is an indispensable physical parameter for calculating the degree of polarization. Since it is relatively difficult to measure the complex refractive index directly, the polarized reflectivity expression of the materials is derived， and an inversion method of surface parameters is proposed when the incident light is linearly polarized based on the existing polarized bidirectional reflectance distribution function of rough surfaces, which can improve the applicability of the complex refractive index calculation. The comparison between the inversion results and the reference values indicates that the inversion method has good reliability.