This paper proposes an optimized lighting design method of light-emitting diode (LED) ring array structure for machine vision, which can obtain high-quality images. The proposed method consists of imaging theory and Taguchi method to obtain uniform illumination distribution. The relationship between image contrast and illumination uniformity is derived based on the imaging theory. Furthermore, the main parameters of illumination distribution are acquired, and simulation experiments are designed in a direct intersection table and simulated using TracePro software. Then, the best parameter combination and influence degree of each parameter on uniformity are obtained; the illumination uniformity of the optimized parameter combination is up to 89.31% in the simulation experiments. Finally, a kind of machine vision light source with excellent performance is designed. Relevant experiments show that the lamp can meet the lighting requirements of machine vision (uniformity is 80.35%). The proposed method is an effective strategy to deal with optical design for machine vision.