For a Cook optical structure with small F number and short back working distance, a channel splitter based on the optical free-form surface and the corresponding test solution are proposed. The solution uses multi-degree of freedom of optical free-form surface to correct the astigmatism caused by tilt of the splitter, which makes transflective two-channel optical image quality approach to the diffraction limit. Computer-generated hologram testing technology is proposed to test the free-form surface of the splitter. The peak valley of the wavefront is 0.0096λ，the root mean square of the wavefront is 0.0017λ in the testing system. The splitter and its testing solution meet the design requirements, and provide practical reference for the optical system with small F number and short back working distance.