The present invention relates to a method for correcting a fragmentary or deformed quadrangular image. The method comprises five steps, i.e. detection of an edge point, elimination of an abnormal edge point, straight-line fitting, vertex calculation and image correction. The method for correcting a fragmentary or deformed quadrangular image is applied to a recognition method and a recognition system for papers, such as valuable documents, bills, identity cards, etc., and can rapidly conduct edge detection and tilt correction on images of valuable documents, bills or papers which are fragmentary or deformed.