The invention provides a paper-plastic composite airbag for pipeline welding argon filling plugging and a preparation method of the airbag. The paper-plastic composite airbag for plugging is composedof a multi-layer paper-plastic composite film. The multi-layer paper-plastic composite film is composed of a water-soluble outer blocking layer/a paper layer/a water-soluble inner blocking layer or formed by repeatedly laminating the structure units above. The two sides of the paper layer are coated with water-soluble blocking materials, and the paper layer can always keep its strength. Accordingly, the paper-plastic composite airbag is endowed with good stiffness, folding resistance and gas barrier property. The paper-plastic composite airbag is bonded to a pipeline through a high-temperature-resistance adhesive to form a high-gas-barrier-property high-heat-stability welding argon filling plugging material. The efficient and reliable argon protection atmosphere can be formed in the limited pipeline of the space, the welding quality and mounting work efficiency are effectively improved, and the construction period is effectively shortened. The paper-plastic composite airbag can be applied to welding construction for gold welded junctions and extra-long-distance pipeline joints of the pipeline and equipment.