The utility model discloses a steel structure movable threshold single-leaf protective airtight door which comprises a door frame and two sets of connecting pieces, and the two sets of connecting pieces are arranged on one side of the inner side wall of the door frame respectively. The door body is arranged on the two groups of connecting pieces; the buffering
assembly comprises a damping mechanism capable of buffering
impact force and an auxiliary mechanism capable of assisting the damping mechanism, and the buffering
assembly is located on one side of the damping mechanism; by arranging the buffer
assembly composed of the damping mechanism and the auxiliary mechanism, the upper end and the lower end of the buffer door plate can be buffered, so that the buffer door plate can buffer
impact force borne by the door body, the
impact force can be weakened, the problem that the door body is damaged due to the impact force is solved, and the service life of the door body is prolonged.