The cutter-workpiece engagement (CWE) is an important basis for accurately predicting milling force and vibration of machining system, which can be dramatically affected by the complex tool path, variable part allowance and various tool profiles. The paper presents a fast calculation method of CWE during peripheral milling process based on the Boolean operation. A second-developed simulation environment embedded the kernel program with the aid of commercial CAM is established. In the computing model, the locally past-cut material entity of the workpiece is replaced by a set of neighboring tools, and the geometric entity of CWE is quickly obtained through the Boolean operation between the tool, workpiece blank, and past-cut entities. The instantaneous uncut chip thickness (IUCT) is further obtained after extracting the tooth start and end cutting angles. Thanks to the first-order computation time complexity, the method has a significant advantage of fast computing speed when compared to the traditional method with a globally updated workpiece. In the milling case of S-shaped workpiece, the results indicate that the method can effectively calculate the CWE status along the entire tool path, and achieve the fast prediction of milling force under a long-time machining condition.