When urgent repair or modification of natural gas pipeline or gas transmission station equipment and facilities are required, it is often necessary to carry out welding and hot work. However, due to internal leakage of valves or gas channeling in the pipe network, it is easy to result in flammable gas release or air ingress at the weld position. Hence it is difficult to guarantee the welding quality. Moreover, the risk of hot work is high. For the above reasons, an auxiliary device was designed for natural gas pipeline welding, which has an independent driver element and can be moved remotely in two directions. The two ends of the draft tube are equipped with air-tight pneumatic tires, which can automatically inflate and deflate. In addition to preventing the risk of fire or explosion caused by the leakage of flammable gas, the positively isolating both sides of the weld inside the pipeline can also eliminate the influence of gas flow and improve the welding quality. The device is suitable for straight pipes with a diameter of 200 mm or elbows with a bend greater than 90°. Field tests have shown that the device responds quickly, is agile, and positions accurately. It achieves a better sealing and drainage effect and can effectively improve welding safety and welding quality in the presence of gas flow.