The utility model relates to an automatic air door, comprising a driving motor, a control circuit, a block board. The driving motor drives the driving worm to rotate, the worm drives the turbine to rotate, and the rotation of the turbine drives a baffle to shield over or depart from the wind port. The turbine shaft, in fixed or moving mode, drives the baffle to rotate or move by the rotation of the turbine shaft or itself, so that the effect of wind port shielding by the baffle or deviation therefrom is achieved. Beneficial effect of the utility model is that the automatic air door can flexibly open or close the wind duct baffle in order to effectively preventing air ventilation between inside and outside, and solve the problem of absolute isolation between inside and outside of the duct.Therefore, wind and other objects are prevented from entering the wind duct from the wind port, and the air door is simple in construction, convenient for installation. Smoke discharging efficient canbe enhanced by over 20% by adopting the air door, and effect is more favorable by adopting a pull type electric air door, wherein no resistance exists on the wind duct block board. A turn-over type electric air door can solve the problem of incapability of using the pull type electric air door due to inadequate horizontal position thereof.