This research first analyze and compiles relevant documents, which serve as the theoretic basis. It then applies the diffraction technology of the X-Ray powder to analyze mineral ingredients of weathered Andesite and ancient Andesite, which has been uncovered by a field study. Results of the research show that influenced weathered Andesite exposed in atmosphere may easily produce Gypsum. XRD is a simple, fast, accurate method to analyze the ingredients of Andesite materials and weathered substances.