1. A pattern matching method, which is used in measurement process for line width measuring machine, comprising: reading 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; respectively comparing 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; determining that the pattern matching is successful if the standard pattern on the measured sample successfully compares with at least one designed original image, and proceeding the subsequent line width measurement process; otherwise, determining that the pattern matching is failed.