. Large automobile cover die with complex characteristics and high hardness after quenching is mainly applied hard milling. In processing, large tool vibration, short cutting-life and much time-consuming increase the die manufacturing cost. In this paper, the relationships of cutting speed with achining efficiency and thickness with tool life are considered in the optimization method. The optimization method based on VERICUT uses the relationships to improve machining efficiency and tool life, thus reduce the large automobile cover die processing costs. The simulation and the optimization laid the foundation for the follow-up physical simulation and experiment.