1. A computer-implemented method for measuring gaps between two parts of an object, the method comprising: (a) selecting two images of the two parts that are jointed in the object, and merging the two images to form an image of the object, wherein one of the two images is regarded as a reference image, and the other image is regarded as a measured image; (b) gridding the reference image and the measured image to obtain triangle mesh surfaces of the reference image and the measured image; (c) obtaining boundary points of the measured image; (d) obtaining outline points of the measured image; (e) obtaining triangles on a joint portion of the reference image and measured points on a corresponding joint portion of the measured image based on the boundary points and the outline points of the measured image; (f) comparing each measured point with an obtained triangle to obtain gap values of the joint portion between the reference image and the measured image, wherein the gap values of the joint portion between the reference image and the measured image are regarded as the gap values of the joint portion between the two parts of the object; and (g) outputting an analysis report of the gap values on a display device.