The baffle door is mainly used to absorb the inlet, exit or bypass flue of the flue gas desulfurization system, or in the system of flue gas denitrification and flue gas dust removal. The air door baffle usually uses a shutter double deck baffle structure, and the air door adopts a special sealing device. The sealing performance is good, and the air leakage rate of the muffler of the blow pipe muffler is less than 0.1%. The actuator can be operated in electric or pneumatic way, and can be operated in a short distance. The opening time and the closing time can be set according to need.