Tiling crystals technology can solve the problem of nonlinear crystal aperture limit in the process of optical parametric chirped pulse amplification (OPCPA). The crystal machining error compenstation is one of the most important problems need to be solved in crystals tiling. The beam quality influenced by tiling crystals machining error is analyzed and the machining error compensation method of tiling crystals is designed. According to the method, an active array mirror system is designed and machined, which is used to compensate the tiling crystal machining error. The feasibility and stability of tiling crystal machining error compensation system is tested, which indicates that the system can satisfy the crystal tiled requirement.