The invention discloses an automatic air stop device for an extruder head wire feed port. The automatic air stop device comprises a square metal box and a metal cover plate installed on the square metal box; the square metal box is provided with a metal bottom plate, an upper metal side plate, a lower metal side plate, a left metal side plate and a right metal side plate, the upper metal side plate, the lower metal side plate, the left metal side plate and the right metal side plate are connected with the metal bottom plate, a metal air stop plate is installed at the roughly central position, in the length direction, of each side plate through fixedly-installed springs, and the surfaces of the four air stop plates are all parallel to the surface of the bottom plate and are located in different planes; a wire feed hole and a wire discharge hole with the same diameter as the wire feed hole are formed in the central position of the cover plate and the central position of the bottom plate reactively, the width of each air stop plate is equal to the diameter of the wire feed hole and the wire discharge hole, an arc groove is formed in the top of each air stop plate, a wire passing channel is formed among the arc grooves in the tops of the four air stop plates, and the center line of the wire feed hole, the center line of the wire discharge hole and the center line of the wire passing channel are located in the same straight line. The four metal air stop plates of the automatic air stop device can stretch and retract automatically according to the outer diameter of a wire core, and thus the automatic air stop device can adapt to feed of wires of different specifications and dimensions without frequent replacement.