Abstract: In view of the problems of low target surface illumination uniformity and insufficient energy utilization rate in the current machine vision detection, the use of LED free-surface reflective cups to replace ordinary diodes for array arrangement was proposed for the first time, and the optimal spacing was optimized to realize the compensation of the center illumination of target surface, reduce the loss of large-angle light source, and improve the illumination uniformity and energy utilization rate in the light source array system. In the free-surface reflective cups light source array, the relationship between the optimal spacing in light sources and the half-light intensity angle and the target surface distance was first theoretically analyzed, respectively. Then, the optimal spacing was calculated when the free-surface reflective cup arrays were rectangular, circular and triangular, respectively, and the corresponding array experiments were compared and analyzed by using ordinary diodes. The results show that under three array forms, the energy utilization rate of the system is higher than 70%, and the illumination uniformity is higher than 89%. Compared with the ordinary diode array, the energy utilization rate is improved by at least 58.6%, and the illumination uniformity is improved by at least 12.8%. Among them, the overall light source of the free-surface rectangular array light source has the highest illumination, and the optimal energy utilization rate is 74.2%, which is 61.9% higher compared with the ordinary diode array. The free-surface circular array light source has the optimal illumination uniformity of 94.1%, which is 15% higher compared with the traditional diode array. The final experimental results show that using the LED free-surface reflective cup light source for array combination, the overall light source effect can be significantly improved.