A new method of determination of thin film anisotropy from the angular dependence of the reflectance interference patterns for s- and p-polarized light is proposed and tested experimentally. The method is based on the different phase angle dependence of polarized light on the incident angle. As a result, the interference patterns of the reflected s- and p-polarized light beams exhibit a different number of oscillations in their angular dependence. The high sensitivity of the method is shown by its application to the interference patterns of a specially prepared multilayer structure with a calculated anisotropy.