In order to settle the problem of selecting milling parameters during milling the workpiece of easy to be distorted,a method for optimizing the milling parameters was proposed based on gray theory.Cutting experiments were designed by orthogonal experimental design technique.The gray relational degree and the gray incidence coefficient among the milling parameters,the machining distortion,the surface roughness and the machining efficiency were calculated.The optimization of the milling parameters was done based on the single objective function and the multi-objective function,and the additional production experiments were completed.The results show that the machining distortion is 0.055mm, the surface roughness is 0.7964μm and the machining efficiency is 36.3mm3/min by means of the optimized parameters, the machining efficiency and the machining quality are improved greatly.