The presented optimization method partitions cutting depth and cutting width was obtained from NC simulation into sections for the NC machining parameter optimization.All cutting steps within one section formed a machining feature combination step.The multi-objective optimization models were set up within each machining feature combination step to optimize the machining parameters,based on genetic algorithm. The machining parameters in NC programs were auto-modified to reflect the optimization effect. The experimental result of NC machining shows that the proposed optimization models and algorithm are satisfactory.