In order to improve tool life for hardened steel SKD11 during the milling process, the related milling experiments are carried out and the influence of cutting parameters on tool life is analyzed based on range method. It is found that the influence of axial cutting depth on tool wear is pretty strong, and the influence of radial cutting width on tool wear is very weak. Based on the milling experiments, the mathematical model of tool wear is established by using of regression analysis method. In order to solve the actual milling problem, the cutting parameters are optimized by using of SQP optimization method based on MATLAB software. During the optimization process, the machining efficiency and the tool wear quantity are set as the objective function. The optimized cutting parameters could greatly improve the machining efficiency in the premise of ensuring smaller tool wear, and it provides the important theory evidence and case reference for NC machining enterprises to reduce compositive production costs.