Abstract: The diffraction properties of two types stainless stain were discussed.To clarify whether the two diffraction peaks during the process of 2θ scanning of austenite stainless steel diffraction,can be the basis of the stress measurement,two different austenite stainless steels—0Cr18Ni9(raw material),1Cr18Ni9Ti(stress relief annealing) and martensitc stainless stain.(A335P92) were measured for many times in this paper.They were demarcated by equal intensity girder method and detected by X-ray system and electromotive method respectively when gradually loaded by using a modified residual stress detecting equipment,self-edit measuring software and based on the monitoring and disposingl function in spots during diffracting process.Then the X-ray diffraction characteristics were obtained by comparing with theoretical values.The results show that austenite and martensitic stainless steel reflect the different characteristics of the diffraction.Although at 127°,corresponding to crystal face(220),K_α diffraction peak of austenite stainless steel is strikingly marked,and two peak locations—the half-width and parabola are accurate,the precision is poor and the stress calculated from this peak does not represent the actual stress according to this peak.However,although K_β diffraction peak at 149°,corresponding to crystal face(311),in spite of the lower peak-back ratio,149° K_β can be the basis to calculate stress after the stress constant was modified.Martensitic stainless steel shows the diffraction properties which are close to that of α-Fe,and the difference between the stress constant acquired by martensitic stainless steel calibration and that of conventional α-Fe is 7.8%.