Based on classical mechanics theory and metal cutting theory,the mathematical model of cutting force of vertical milling cutter in high speed cutting was established. Taking the vertical milling cutter in high speed cutting as the research object,finite element software ANSYS was used to analyze change laws of cutting stress and strain of end milling cutter in different cutting conditions, the change law of cutting force with the cutting parameters was gained. It provides reference for finite element analysis, influencing factors analysis of cutting force and initially revealing the cutting mechanism. At the same time it provides theoretical support for efficient use of enterprise CNC equipment, as well as the selection of cutting parameters by workers.