In the multistage machining processes (MMPs), SPC is widely utilized to control the quality of machining processes and diagnose the processing error. But there is a defect, that it can not compensate the error when the machining process is abnormal. For this issue, a new method of quality diagnosis and error compensation is proposed based on EPC (engineering process control). A new framework for processes quality diagnosis and error compensation about the description of machining processes and controlling mechanism of machining process quality is proposed first. And the mapping model of machining error propagation is introduced to explore the model of the error compensation decision. From theoretical level, modeling level and solution level, the mapping model from the decision model based on EPC to SPC is studied, in which the key technologies are the machining error propagation model and the error compensation model. Therefore, the machining error propagation network is utilized to build the error propagation model, and an adaptive control method based on the stability theory is introduced to make error coordination optimization.