Abstract: A method for manufacturing a novel air permeable composite film is disclosed. The air permeable composite film has a polymer layer with a top face and a bottom face and a sealing layer covering the top face. The polymer layer is first perforated by virtue of an impression process to form a plurality of tiny gaps in it for air permeation. Then the sealing layer is coated on the top face of the polymer layer to fill the gaps. The differential pressure between the top face and bottom face of the polymer layer enlarges the gaps and makes the gaps become air permeable.