Photocurrent scanning imaging （mapping） technology is a key technique in the research of solar cells and photodetectors. However， traditional galvanometer-driven beam scanning methods are limited by a restricted scanning range and image distortion. To address these shortcomings and meet the need for testing the photocurrent uniformity of large-area optoelectronic devices， an automated photocurrent mapping testing system has been developed based on optical component scanning. This system offers a large imaging range， high spatial resolution， high stability， and low cost. With its high-precision mode， it can achieve sub-micron geometric positioning （subdivision number 6400， scanning step size 0.625 μm）， fulfilling both large-area scanning requirements and providing high-resolution testing. Moreover， its simple structure greatly reduces the overall cost of the mapping system. Using a silicon solar cell sample with a white paper surface covered by the character “南” （south） or an encoder strip mask， it was demonstrated that the scanning range exceeded 10×10 mm2， with a spatial resolution of 0.6 μm. The system was also used to characterize the surface photocurrent images of Cu?ZnSnS? and Cu?ZnSn（S，Se）? solar cells. The results show that the Cu?ZnSnS? cell contains more defects， while the Cu?ZnSn（S，Se）? cell exhibits a more uniform surface photocurrent response with fewer defects. These findings contribute to the optimization of solar cell fabrication processes.