The self-enhancement of diffraction was obtained due to the light crawling effect by reducing the thickness of the Ce:Fe:LiNbO3 and by increasing the diameter of the pump beam. Lighting the crystal by a single beam, the phenomera of variation of the light polarization, i. e. the anisotropy self-diffraction from o-light to e-light or from elight to o-light were observed, and the machenism was discussed.