The invention relates to a pneumatic quick-open air door cover which comprises a door cover body (1), a back plate (3) and two side plates (4), wherein the door cover body (1), the back plate (3) and the two side plates (4) form a trapezoidal cavity; the cavity is filled with a fireproof lining (2) which is made of ceramic fiber cotton. According to the pneumatic quick-open air door cover, the trapezoidal cavity is defined by the door cover body (1), the back plate (3) and the two side plates (4), so that the air door has good sealing property when being closed; meanwhile, the cavity is filled with the fireproof lining, so that the thermal insulation effect of the door cover is good, the heat loss of the heating furnace is small and the thermal efficiency is high.