Abstract: In order to reduce the residual stress of quenched S35VN tool steel and improve its overall performance to meet the final use requirements, it is necessary of quenched S35VN for tempering.X-ray diffractometer and scanning electron microscope were used to study the differences of phase and microstructure of quenched S35VN steel after tempering at 180℃, 200 ℃and 220 ℃, respectively, and their effects on the hardness, tensile properties and corrosion resistance of the alloy were studied.The results show that the matrix of S35VN steel is mainly martensite after three kinds of temperatures, mixed with a little residual austenite, and the carbide type is mainly M₇C₃, containing a little M₂₃C₆ and MC.The hardness of the alloy decreases, while the strength and plasticity of the alloy increase.After tempering at 180 ℃, the average hardness is 56.5 HRC, the average tensile strength is 1844 MPa, and the average total strain at fracture is 3.89%, indicating the best corrosion resistance.