The invention discloses a VIN (vehicle identification number) code checking method, which comprises the following steps that: 1, an image comparison module is used for positioning VIN codes in a source image, a threshold is determined by adopting a maximum between-class variance method, and the VIN codes are positioned; 2, the image comparison module carries out horizontal angle correction on the VIN codes in the source image, and the height values of the VIN codes are obtained through image rotation; 3, the image comparison module carries out inclination angle correction on the VIN codes, and VIN code images with the consistent height are obtained; 4, the image comparison module extracts the position of each character in the VIN codes through segmentation, and the processed source image is obtained; 5, a tested image is retrieved, the first to fourth steps are repeated, the processing on the tested image is completed, and a processed tested graph is obtained; 6, the image comparison module carries out matching comparison on a picture, the processed source image and the processed tested image are subjected to template position matching and are compared, whether the contents of each character are changed or not is judged, and comparison information is obtained.