Abstract: In the image processing of machine vision, there are many factors affecting the image quality, and one of the main factors is the illumination angle of the light source. In order to get the better image data, it is necessary to carry out the simulation analysis and experimental study on the optimal angle of the light source illumination in the vision system. A single-variable method was used in the experiment to change the illumination angle of the light source only. Through a combination of the theoretical calculation, the simulation, and the experimental verification, the best illumination angle of the light source was obtained. The image edge quality under the optimal angle and other angles was examined in combination with the Sobel algorithm. The results show that the performances of image illumination data and edge image are the best under the illumination angle of 57.17°, which are of guiding significance for deeper image processing and image acquisition.