The invention provides a full-through gas-radiation rear window decoration strip and a machining method thereof, wherein the full-through gas-radiation rear window decoration strip comprises a decoration strip body which is of a U-shaped structure; nitrogen is blown to the two ends of the decoration strip body from the middle position of the decoration strip body so that the interior of the decoration strip body is through from end to the other end. The full-through gas-radiation rear window decoration strip and the machining method thereof have the advantages that the weight of the full-through gas-radiation rear window decoration strip can be reduced because the interior of the full-through gas-radiation rear window decoration strip is machined into a full-through structure in case of guaranteeing the strength requirement; therefore, material cost is reduced and the weight of the whole vehicle is also reduced.