Abstract: In order to realize the additive preparation and surface repair of high strength bainitic steel parts, amedium-carbon high strength bainite steel was prepared by laser powder deposition and salt bath isothermal treatment with different process parameters. The alloy composition (mass fraction) was Fe-0.0029C-0.0150Si-0.0150Mn-0.0096Cr-0.0120Ni-0.0100Al-0.0050Mo.The microstructure of the steel wascharacterized by scanning electron microscope and X-ray diffraction, and the mechanical properties of steel were tested through tensile testing machine and Vicker's microhardness tester. The effect of isothermal temperature and isothermal time on microstructure and properties of the steel during salt bath isothermal process was analyzed. The best integrated mechanical properties were observed after deposition and salt bath isothermal at 280℃ for 5h, the average microhardness, tensile strength, yield strength, andelongationwas 494.5HV, 1248MPa, 1037MPa, and 14.5%, respectively. The results showe that the microstructure of the samples with different process parameters is composed of lath-like bainite and retained austenite, and the microstructure is uniform without defects such as carbide, segregation, pore and inclusion, but too low isothermal time or too high isothermal temperature would lead to the deterioration of the microstructure. This study provides a reference for the additive and repair of high strength parts.