Abstract: The structure and mechenical properties of Φ52 mm 45MnVTi steel finished rolling at 917～922  ℃ and water-cooling-self-tempering with 680～830 ℃have been tested and researched.Results show that the microstructure of asprepared steel consists of ferrite and pearlite,with the decrease of self-tempering temperature,the yield strength and tensile strength of steel gradually increase,and toughness increases at first and then decreases. When the range of self-tempering temperature is 750 to 770 ℃,the microstructure of steel products is fine ferrite and pealite, and the test steel average value of tensile Strength 841 MPa,yield Strength 547.5 MPa,impact energy 50.5 J with an optimal match between the strength and toughness of steel and pearite lamellar spacing 2.39 μm,to meet the use requirements.