The exhaust analysis of a new type of car with hatchback tail door is carried out in the drawing stage, and the sheet metal structure of the upper part of the hatchback tail door is modified, so that the gas at the top of the hatchback tail door can be completely discharged during the pretreatment electrophoresis process, thus avoiding the gas accumulation between the inner and outer plates of the upper part of the hatchback tail door, thus ensuring the hatchback tail. The quality of the electrophoretic paint film on the upper part of the door prevents the rust on the upper part of the hatched tail door and improves the service life of the upper part of the hatched tail door.