Dunnage bags are creative and simple protecting tools in transportation which are made of high-strength Kraft paper wrapped in PP and PE, its toughness and reliable. The inner shell is made of five layers of coextrusion films, mainly PE. Back valves are convenient in their operation of inflation and deflation. They are also airproof and solid, so that they can effectively prevent cargo collisions in truck, container or railway transport. Air bags can fully fill the space between cargoes, support the weight generated by jolt and weaken vibration to protect goods from damage in transport. They are better than any other supports, fillings or protectors, and more environment-friendly than traditional materials.