Abstract: Laser shock peening was conducted on the surface of 45 steel specimens under different laser energy (4, 6, 8 J). The effects of laser energy on the microhardness, residual stress, microstructure and friction and wear properties of the specimens were studied. The results show that with the increase of laser energy, the degree of lattice distortion, compressive residual stress, microhardness and wear resistance of 45 steel were improved. Under the laser energy of 8 J, the surface (211) crystal plane full width at half maximum, residual compressive stress and microhardness of 45 steel increased to 3.5°, 500 MPa and 345 HV, and the friction coefficient and the wear mass loss decreased to 0.61 and 157 mg, respectively; the wear surface had the least peeling material, and the depth and width of the furrow were the smallest. The improvement of friction and wear properties of 45 steel was mainly due to the high-density dislocation and high-amplitude compressive residual stress induced by laser shock peening.