Initial permeability of Fe-Si polycrystalline thin films was investigated. From calculation of magnetocrystalline anisotropy and initial permeability assuming that the magnetization is confined in a certain crystal plane, Fe-Si polycrystalline thin films with (111) orientation parallel to the film plane are expected to have high permeability of about 5000. Fe-6.9 wt%Si films were deposited on three kinds of underlayers with three different crystal orientations. Initial permeability of Fe-Si films on ZnSe underlayers with (111) orientation is about 1700, which is higher than that of the films with (100) or (110) orientation.