Embodiments of the invention disclose a mask plate and a method for detecting an exposure defect using the mask plate. The mask includes a mask pattern, and the mask further includes a plurality of detection-mark mask patterns arranged along a scan direction of an exposure machine, the detection-mark mask patterns are arranged at an edge of the mask pattern. The detection-mark mask patterns are adapted for forming detection marks on a substrate. The detection marks are adapted for reflecting exposure defects of the exposure machine. With the mask plate of the invention, the reason for the exposure defect may be precisely decided, thereby improving the exposure effect and improving the parameter index of the substrate.