Abstract: A liquid simulated eye was designed to detect different spherical diopter indexes in the type inspection of medical equipment vision screening instrument. This liquid test simulation eye design is composed of three parts: lens, cavity and retina-imitation piston. By using the principle of geometric optics and the optical scattering effect of human retina, the relationship between the accommodation displacement of the designed adjustable liquid simulated eye and the spherical mirror power was calculated and analyzed. The designed liquid test simulated eye can be applied to vision screening instruments, computer refractometers and other optometry equipments based on photography principle in spherical lens measurement and so on.