The invention discloses a method used for detecting polysilicon solar energy battery piece EL image surface dark patch defects. According to the method, binaryzation extraction of a target battery pieces is carried out based on a battery piece EL image collected using a near infrared camera, image segmentation is carried out through a region growth mode based on complex and various background interferences caused by polysilicon so as to obtain possible defect connected domains; two methods are adopted for elimination of false detection, wherein according to one method, connected domain analysis is carried out so as to extract connected domain area and opening area characteristics, and according to the other method, the images corresponding to the connected domains are subjected to curve detection so as to eliminate false detection through image texture analysis. The method is capable of determining solar energy battery piece dark patch defects accurately, and realizing locating of darkpatch defects.