The traditional material constitutive model can effectively simulate the mechanical properties during the cutting process. However, the scale characteristics contained in materials are not considered in the traditional cutting model, and the inherent scale effect of materials is also ignored. Therefore, the traditional cutting constitutive model cannot effectively reflect the size effect in the cutting process, and then cannot obtain the accurate stress, strain, and temperature. In this present paper, a material constitutive model which can reflect the scale effect is established based on the strain gradient plasticity theory. Through the established model and secondary development of abaqus, the two-dimensional dynamic finite element simulation model of cutting Inconel 718 is established. By comparing the cutting experiment results with the simulation results, the established simulation model can more accurately reflect the effects of temperature, strain gradient effect, equivalent stress, and its scale effect on cutting deformation during the machining process.