Based on the model of anisotropic coupling theory,the initial intensity ratio of the two recording waves which was coherent to the length of the grating was introduced to the anisotropic coupling equations. The anisotropic Bragg diffraction properties of volume gratings in photorefractive crystals were investigated by the method of the couple wave theory. The effect both of the initial ratio of the intensity and of the recording angles of writing waves on the anisotropic Bragg diffraction properties of volume gratings was discussed. It is shown that both the ratio of the initial intensity and the incident angle of the writing waves were selective for the anisotropic Bragg diffraction efficiency of the volume gratings,while these two recording conditions were not selective for the isotropic Bragg diffraction.