<p>In the cutting process of nickel-based superalloy (Inconel718), the cutting deformation is complicated, forming sawtooth chips, and the study of its deformation mechanism has always been a hot issue in the academic circle. Numerical simulation provides an effective analytical means for in-depth understanding of the cutting process, but the current simulation methods still have some limitations in terms of cross-scale simulation ability. The dislocation evolution and deformation process in the cutting deformation of Inconel718 are still not well understood. In this paper, we propose a cross-scale material plasticity deformation simulation framework in which three-dimensional discrete dislocation dynamics (3D-DDD) coupled with base dislocation density (BDD) equations. Finite element simulations were performed by this simulation framework to study the stresses, strains, cutting forces, and temperatures during machining, as well as the microstructure evolution under different cutting conditions, such as grain size and dislocation density distribution evolution. In the process of cutting Inconel718, high-density dislocation movement and grain refinement mainly occur in the primary deformation zone and the second deformation zone, and the grain refinement degree of the machined surface is relatively weak. With the progress of cutting, the average grain size of chips is significantly smaller than that of the workpiece matrix, and the grain refinement in the chip shear zone is the most obvious. Strain rate plays a leading role in grain refinement. At the same time, due to the temperature rise, thermal softening occurs, grain deformation and dislocation accumulation in the shear zone cause cracks and holes, and accelerate the formation of sawtooth chips. Through experiments and simulation, the deformation mechanism of nickel-based superalloy is demonstrated, which further promotes the understanding of the microstructure evolution of Nickel-based superalloy during high-speed cutting.</p>