The surface yield strength of S30432 austenitic steel after conventional and dual shot peening treatments has been investigated by means of X-ray stress analysis. The results showed that the proof stress sigma(0.2) of the shot peened surface increased to around 830 MPa and 940 MPa after conventional and dual shot peening, respectively. While for the bulk S30432 austenitic steel, the yield strength was 268 MPa. The strengthen mechanism was discussed in terms of microstructure by X-ray line profile analysis method. The results revealed that the refined domain size and high micro-strain were induced in the deformed surface layer. This changed microstructure was mainly responsible for the high yield strength of shot peened surface. The surface yield strength of the material surface can be obtained from the proposed X-ray stress analysis method. Therefore, this method can be considered as a complementary approach in investigating the microstructural hardening effect of SP treatment. (c) 2012 Elsevier B.V. All rights reserved.