Abstract: In order to make a real and effective numerical simulation of the dynamic rounding process of the workpiece in the centerless grinding system and make a scientific and reasonable prediction of the final roundness of the workpiece, a dynamic rounding model of centerless grinding considering the instantaneous position change of the workpiece center is established and numerically simulated. Firstly, the influence of the center displacement of the workpiece caused by the change of the surface morphology of the workpiece during the grinding process and the center displacement of the workpiece caused by the vibration of the grinding system on the instantaneous position change of the workpiece center is analyzed. Then, considering the mutual coupling between the grinding wheel and the workpiece in the centerless grinding process and the material removal relationship, the dynamic rounding model of the workpiece grinding is established. Finally, the dynamic rounding model and the iterative algorithm for simulating the material removal and roundness change of the workpiece are used to simulate the dynamic rounding process of the workpiece, and the whole process of material removal and contour formation of the workpiece is reproduced. Through the analysis of the simulation results, the authenticity and rationality of the proposed centerless grinding dynamic rounding model and iterative algorithm are confirmed, which has certain guiding significance for the study of centerless grinding rounding process.