Aiming at the cutting parameters of turning and grinding for slender shaft,a mathematic model was established,which was based on the minimum process cost of turning and grinding.The model was constrained by the stiffness of the workpiece and the tool bar,the strength of the turning tool and the lathe feed system,the power and parameters of the machine tool,the machined surface roughness,and the total machining allowance.The variables of the model included the cutting speed,the feed rate,the back engagement of cutting edge,the rotate speed of workpiece in grinding,the allowance of grinding,the axial feed and radial feed of grinding.An experiment case of a motor shaft was performed to verify the validity of the optimization model.Turning and grinding parameters were optimized by using the MATLAB pattern search toolbox.Compared with the traditional selection method of cutting parameters,process costs can be reduced by more than 35%.