Abstract: The problems of long production cycle, high resource consumption and dim paint film color in the existing process of rail transit vehicle sliding plug door panel waistline color separation are analyzed. It is proposed that the door panel waistline color separation process be moved forward to the manufacturer, quality control measures are proposed under the premise of strict process standards, and the height deviation of door waistline and body waistline is determined not to exceed 5 mm. The spraying test results show that the optimized process has good coloring effect and the carbody color band has overall consistency without increasing the production cycle.