Abstract: Non-uniform light source and wide field angle were two causes for illumination non-uniformity of image plane in photoelectronic image testing system. To study the influence, the relationship model between spacing of LED light source and image plane illumination was built. The influence of different LED intervals on image plane illumination was simulated and analyzed. The relationship model between opening angle of object plane of optical coupling system and image plane illumination was established, and the influence of opening angle of object plane on illuminance uniformity of image plane was simulated and studied. The experiment results show that non-uniform light source and wide field angle are two main causes for non-uniformity illumination of image plane, which provides the theoretical basis for designing better corresponding correction algorithm.