Machining deformation and the low yield rate in machining process of thin -walled workpiece problems have mainly affected the processing precision of parts and productivity. Therefore, it is of great significance to study the deformation error and the low yield rate of thin -walled workpiece processing in the theory and practical application. The main influence factors of quality of process in numercial control（NC） machining were analyzed by means of experimental study and finite element analysis （FEA） in combination. In the process of machining, for the deformation of thin -walled workpiece, some key factors including machining process, assembly plan, cutting tools selection and machining trace were discussed to control the deformation in thin -walled workpiece, and to strengthen the concrete measures for improving the rigidity of the process. The machining efficiency and quality are improved.