Abstract: X-ray diffraction (XRD) is a convenient and non-destructive method of measuring residual stresses on the surface of metal. According to the principle of using X-ray method to measure the residual stresses,diffraction intensity “anticlimax” phenomenon is primary discussed in the experiment,and the reasons of the phenomenon and processing techniques of determining peak positions are analyzed detailedly. It is an reference to improve and develop X-ray diffraction analysis of residual stresses with welded aluminium alloy.