Abstract: The cross section surface of 0Cr18Ni9Ti stainless steel bar was treated for nanograins by means of high energy shot peening(HESP).The microstructure and properties of the plastic deformation layer were characterized by using scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffraction(XRD) and microhardness tester.Results show that nanograins with less than 100 nm were gained at the range of 70 μm to the top surface.From matrix to treated surface,the microstructure of the deformation layer was in turn single-phase austenite,double-phase microstructure and single-phase martensite.In the plastic deformation layer the microhardness increased significantly because of the grain refinement.