Abstract: The side wall component is one of the core components of the high-speed EMU aluminum structure. Due to the technical requirements of the deflection of the whole vehicle, it needs to be welded and processed with prefabricated deflection. Developing a side wall processing technology that can accurately compensate for deflection changes and complete the process quickly and effectively is the key to comprehensively improving the processing capacity of aluminum structure large components. The process development, fixture design, tool selection, process flow and 3D simulation verification of CNC programs for side wall processing are studied.