This paper proposed a projection splicing photo-alignment technology based on a liquid crystal on silicon spatial light modulator (LCOS SLM). By combining SLM and two-dimensional translation stage, the fabrication of liquid crystal optical elements with arbitrary size and arbitrary Pancharatnam-Berry phase pattern can be realized. Based on this technology, a variety of liquid crystal optical elements were fabricated by continuous scanning exposure method, such as one-dimensional polarization grating, two-dimensional grating, microlens array and hologram. The experimental results show that: this technology can realize the fabrication of optical elements with continuous phase distribution and enlarge the aperture of optical elements; the diffraction efficiency of a one-dimensional polarization grating with a size of 25.4 mm×25.4 mm reaches 98.32%, and the error in each area does not exceed 1%; the liquid crystal optical elements with two-dimensional periodicity or other complex pattern can be fabricated only by changing the exposure pattern loaded to the SLM. The SLM-based projection splicing photo-alignment technology has the characteristic of high resolution, high efficiency, simple process, and can realize the fabrication of optical elements of any scale, which can further promote the development and practical application of liquid crystal optical elements.