Abstract: To investigate the cutting mechanism of the titanium alloy TC4 in the ultra-precision cutting process, an orthogonal cutting finite element model was established. The key techniques of modeling the FEM model and the material model were introduced detailed. The ultra-precision cutting process of titanium alloy was simulated using the established FEM model. The chip formation, cutting force and cutting temperature were obtained. To validate the simulation, an ultra-precision turning experiment has been carried out by single point diamond turning machine. Through the comparison of chip formation and cutting force, the result of simulation agrees with the result of experiment. It proves that the FEM method is an effective method can be used to investiate the ultra-precision cutting mechanisms of titanium alloys.