In order to obtain the optimum cutting parameters of hardened 25CrMo4 steel, three-dimensional (3-D) finite element model (FEM) was built with the aid of Deform-3D software and the cutting process was simulated.Variation law of cutting temperature under different cutting speeds, back cutting depths and feeding amount was obtained, and the optimum cutting parameters were obtained through evaluation of the simulation results. Cutting experiments were carried out under the optimal cutting parameters and the experimental results show that the cutting temperature increases along with the increasing of the cutting speed, feeding amount and cutting depth; in addition, the experimental values of cutting temperature agree well with the simulation results under different cutting speed, which indicates that cutting temperature is the most important physical parameter for optimizing the cutting parameters within the range of cutting speed used in the experiment.