Abstract: s-polarization and p-polarization will separate when thin-film filters are used in tilted incidence. Central wavelengths of the two polarization beams do not coincide with each other and pass-band width of s-polarization is less than that of p-polarization. However, the polarization characteristics of the two polarization components in incidence angle can be coincided by adopting film system architecture meeting specific conditions with more than two kinds of materials. Above all, two equations on the polarization componentsreflectivity are given based on theoretical analysis. Requirements for depolarization can be found from the expressions. Then, the refractive index of the materials can be obtained. Thus, we can design depolarization film system architecture. Finally, the simulation calculations of a filter design composed of 129 layers for three cavities prove that the method is feasible.