Abstract: It has been performed to measure depth distributions of residual stresses and half width values of strengthened tapered rollers and retained austenite at the surface with X ray diffraction technique. The experiment results indicate that there are residual compressive stresses in strengthened surface layer of tapered rollers and residual compressive stress peak can be found at a depth of around 200 μm from surface,which increases with strengthening time and up to maximum when strengthening time is 16 h,decrease when strengthening time over 16 h. And half width values of the rollers at surface and subsurface decrease during strain strengthening,and there is a minimum at depth of 50 μm or so.