Abstract: ANSYS software was used to simulate and calculate the variation of temperature field of laser quenching on 45 steel surface to predict the depth and width of hardening layer.The influence of process parameters on the temperature field of laser quenching on 45 steel surface was analyzed, and the relationship between process parameters and the depth and width of hardening layer on 45 steel surface were discussed.The results show that the depth and width of the hardened layer on the surface of 45 steel are proportional to the output power of the laser and inversely proportional to the laser scanning speed and the diameter of the spot.The optimum technological parameters of laser quenching on 45 steel surface are laser output power 900 W, laser scanning speed 8 mm/s and spot diameter φ5 mm.The depth of the hardened layer is 0.508 mm, and the width is 2.865 mm.