A method was presented to analyze the computer-numerical-control (CNC) milling process based on characteristics of the curvature of curved surface. It applied differential geometry theory to CNC milling process. This method was employed to analyze the effects of the curvature attributes of isoparametric curves on the interference and cutting width during the process through planning the cutting path on the constructed free-form surface and establishing cutting path isoparametric curve. At the same time, according to the research on the relationship among the cutting path, the scallop height and the attributes of curvature of curve, some laws affecting the machining efficiency, accuracy and interference were obtained. In addition, the research shows that the cutting width can be improved effectively by optimizing the anastomosis curve of the cutting tool radius, the scallop height and machined surface's curvature. The experimental results show the effectiveness of the method in analyzing CNC milling process based on the attributes of the curvature of curves,the machining efficiency can be increased 5%~8%.