Abstract: How to calculate the intersection points between line and cutter swept volume (CSV) is a core problem in NC program graphical verification and machining process simulation techniques. According to the characteristics of 5-axis machine tool, the paper presents a novel intersection algorithm by decomposing the CSV into several simple surfaces, and the intersection point is found by composing the intersection points between line and simple surfaces. Based on this method, a simulation software which is used to verify the precision of 5-axis NC milling is implemented, and the validity of the system is confirmed by the practice of manufacturing and simulation. The method is very useful to the machining process simulation system.