With the rapid development of China's printed circuit board (PCB) industry, the detection of defects in bare boards is of crucial importance for enhancing production quality and holds significant research and application value. Given the limitations of existing detection methods, such as the low accuracy in detecting minor defects, this paper proposes a method for detecting minor surface defects on PCBs based on photometric stereo technology. This method involves obtaining four images of the target object under varying lighting conditions, utilizing image processing algorithms to extract photometric stereo information for calculating the surface normal and reflectance properties of the target. Subsequently, it analyzes the three-dimensional shape and position of surface defects, achieving comprehensive capture and precise detection of minor defects on the PCB surface. The results indicate that this method offers higher detection accuracy and holds crucial significance for improving the quality control level in the PCB manufacturing process.