1. A pattern matching method of a pattern matching apparatus, which is used in measurement process for line width measuring machine, comprising: using an image acquisition unit to read a standard pattern used for matching on the at least one predetermined position of a measured sample, and the measured sample being a transparent substrate coated with multiple patterns; using a matching processing unit to compare each standard pattern of the measured sample with prestored multiple designed original images corresponding to the standard pattern, and the difference within the multiple designed original images being the gray-scale; comparing the standard pattern on the measured sample with each corresponding designed original image, determining that the comparison between the measured sample on the standard pattern and the designed original image is successful if a similarity of at least one reaches a predetermined ratio, wherein the similarity reaching the predetermined ratio can be preset; otherwise, determining that the pattern matching is failed.