The invention relates to a method for detecting the defects of chain belts of a zipper on the basis of digital image processing, belonging to a novel technology in the technical field of appearance quality inspection of zippers in the hardware industry. According to the method, a detection device consisting of a target positioning and triggering device, an image acquisition sensor, a conveyor belt driving device, a background light source device, a feed belt, a sorting device and a PC (Personal Computer) machine or an embedded control system is utilized to carry out detection; and a zipper product to be detected is fed into a feed belt platform of the detection device and is then fed to a detection region under the drive of the driving device, then the zipper product is subjected to target positioning by the target positioning and triggering device, a chain belt digital image of the zipper is acquired by the image acquisition sensor, the image is transmitted to the PC machine or the embedded control system, the target image is processed by the PC machine or the embedded control system, and whether a chain belt region of the zipper has the defects is compared and judged according to a processing result and the judgment standard. The method has the characteristics of simple detection process, high detection speed, high detection accuracy and the like.