Abstract: In order to improve the detection efficiency of metal surface defects, a detection method based on four light source photometric stereo method is proposed. Firstly, CCD camera is used to collect images of four perforated metal samples from different spatial angles. Secondly, HALCON operator is used to calculate the surface gradient image based on the principle of photometric stereo technology of four-light-source, then it is converted to the average curvature image. Finally, the curvature value of each point of the image is converted to gray value, and the global threshold is used to segment the defect area. Compared with the classical photometric stereo method, the results show that the four-light-source photometric stereo method can accurately construct the surface gradient information of the image, and the average curvature information of the image can be used to detect the defects of the metal surface quickly.