Abstract: In the process of detecting the flatness of stainless steel vehicle side walls, to reduce the appearance quality problems caused by the secondary scratches and meet the requirements of the next process, a detection scheme of the vehicle side wall flatness is proposed. In which, the upper part of the vehicle side wall doors, the space between two windows, the vehicle cross section and others are classified as different areas, measurement methods and testing requirements that match each measuring area are adopted. Measuring tools and testing sample patterns for the two directions of side wall plane and vehicle section, the analysis of flatness detection, the test standards and measurement requirements are introduced. The results show that the flatness measurement of vehicle side walls needs to be completed simultaneously from the plane direction and the section direction, the dent depth of welding joint can be adjusted by changing the welding parameters.