Abstract: Crankshaft inner milling technology is widely used in crankshaft rough machining because of its advantages in machining quality and efficiency. However, the selection of internal milling parameters is lack of corresponding standards and methods. In this paper, through the finite element simulation, a finite element model of crankshaft inner milling is established. The simulation of crankshaft deformation is implemented by using the milling force obtained from the inner milling simulation so as to predict the cylindricity error of crankshaft journal. It is revealed that the cylindricity error of crankshaft journal decreases with the increase of cutter speed, and the rate decreases gradually.