Abstract: To utilize a control chart effectively, the exponentially weighted moving average (EWMA) method is introduced in to forecast the linear variation of shaft diameter resulting from tool wear. Based on EWMA, the MCEWMA control chart is proposed to monitor tool wear process, i.e., the moving center-line EWMA. In the whole service life of a tool used in machining process, the tool wear and relevant random fluctuation are both regarded as the common causes in tool wear monitoring process, thus avoiding the frequent false alarm when using conventional control chart. An example is given to illustrate the criterion for selecting chart parameters.