To improve the quality control effect and decrease the manufacturing cost in the product’s multistage machining processes, based on the quality loss of single stage machining process, an overall mean quality loss model of multistage machining processes is established by the integration of Duncan cost model, Taguchi quality loss model, mean shift index and average time to signal (ATS). By using this quality loss model, the overall mean quality loss optimal function of multistage machining processes is constructed and the control parameters of this function are optimally solved. Besides, The Shewhart control chart and Cause-selecting control chart can be optimally designed with the control parameters of this optimal function. Finally, on the basis of an application, the multistage machining quality control based on minimum overall mean quality loss is verified to improve the control chart’s performance under the condition of the minimum overall mean quality loss.