Abstract: From the features of NC turning process, a workpiece decomposition expression model based on the constructed units was put forward, and Boolean subtraction was performed using this model and a tool solid model to simulate the real-time process of cutting and validate the simulation result. Based on the above and the principle of cutting force and chip generation, cutting parameters and some related parameters in geometric simulation, such as cutting depth and cutting velocity, were extracted and used in the calculation of cutting force and the simulation of chip. This NC turning machine simulation system is the integration of geometric and physical simulation.