Abstract: The optical system has been established in which the change of polarization state for magneto-optic crystal can be measured.In the system,the rotation angles for two types of magneto-optic crystals (BiCaInVIG and GdYBiIG) used in optical communication system have been measured at oblique incidence.The experiment results show that there is anisotropic distribution of Faraday effect in the magneto-optic crystal.