Abstract: Corner cube prism is a high precision component which is often used as a cooperative target of the laser rangefinder, in which the errors of three rectangular angles of a corner cube prism influence directly the rangefinding range and the rangefinding precision of the laser rangefinder.So the errors of three rectangular angles of corner cube prism must be strictly controlled in its polishing progress, in which the error testing method of corner cube prism is the important means to guarantee its quality.A photoelectronic testing system of rectangular angle error of corner cube prism based on inclined incidence method is presented in this paper. When a parallel beam travels to the inclined surface of corner cube prism without any errors at an incident angle () where n is the refractive index of corner cube prism, the refracted beam will be perpendicular to two rectangular surfaces, and the outgoing beam, after two successive reflection of the rectangular surfaces, will be parallel to the original incident beam.If the angle of two right surfaces of corner cube prism exits an error, there is a small angle between the outgoing beam and the incident beam, and the self-collimating dual-image of the reticle at the focal plane of the collimator will be formed.On the basis of the law of reflection and refraction in the vector form, the relationship between the rectangular error of corner cube prism and the gap of the self-collimating dual-image is derived in details.Then a photoelectronic testing system in which the rectangular error of corner cube prism can be tested directly using self-collimator is presented.The photoelectronic testing system are improved with a CCD camera, an image assembler, and a PC computer, instead of eyepiece reading system.Finally, the precision analysis of the testing system is given.