High Energy Shot Peening ( HESP) was used to treat the material surface in order to study the effects of nano-crystallization surface of 40 Cr on wear behavior. The nano-crystalline layer was obtained on surface. Micro-structure after HESP was analyzed, residual stress and micro-hardness after nano-crystallization were measured. Wear behaviors of nano-crystalline surface were examined as well . The experiment results show that, HESP causes severe plastic deformation on surface, and the micro-hardness increases by 68 % compared to matrix. There exits compressive residual stress with large magnitude on surface, and the maximum value is-736 MPa, meanwhile, the compressive residual stress layer come up to 0 . 9 mm. The frictional wear experiments show that, HESP nano-crystallization can apparently decrease friction factor, and the wear loss is less than 1 / 5 of untreated samples, HESP largely improved the wear-resisting property of 40 Cr.