Abstract: 4Cr5Mo2V steel specimens were processed by three-pass complex shot peening. The effects of shot peening on the surface morphology, microstructure, hardness, residual stress, and high temperature (100, 300, 500 ℃) friction and wear properties and mechanism of the test steel were studied by comparing with those of un-shot peened specimens. The results show that the shot peening significantly improved the surface roughness of the test steel, and induced an obvious plastic deformation layer, a hardened layer and a residual compressive stress layer on the surface. The wear rate of the test steel after shot peening was reduced by 41.8%, 17.1% and 63.3% at 100, 300, 500 ℃, compared with that before shot peening, respectively. The improvement of wear resistance of shot peened test steel was related with the hardened layer and residual compressive stress layer produced by shot peening. At 100 ℃ and 300 ℃, the wear mechanism of the test steel before and after shot peening was mainly adhesive wear and abrasive wear. When the temperature rised to 500 ℃, the wear machanism was oxidation wear; the shot peened test steel could still maintain high hardness and residual compressive stress, and the surface oxide layer was more dense and stable, therefone only slight oxidative wear occurred.