Aiming at the influence of illumination environment, luminous intensity, detection distance and the number of light - emitting ports on the online maintenance of navigation lights, a visual inspection system based on random Hough transform is designed. Based on the characteristics of the strong backlight image caused by the diffraction effect, the improved random Hough transform is proposed, which is to select the random points by multi-zone assignment and quadrant constraints, and to determine the radius according to the target image contours. The experimental results show that the designed navigational lamp detection system can effectively detect the center of the lamp online, and has good adaptability and validity.