The diffraction properties of liquid crystal (LC) cells fabricated by photoalignment substrates with different periodic optical anisotropic distributions are demonstrated. The twist angle distribution structure inside the LC cells formed by the grating period difference between photoalignment substrates is called "beat structure." In addition to diffraction corresponding to the grating periods of photoalignment substrates, beat structure itself also functions as a diffraction grating. The diffraction properties can be controlled by varying the retardation. The fabrication method and diffraction properties of the LC cells with beat structure are explained by both experiment and theoretical analysis.