The invention discloses a tail-towing gas protective cover for welding. The protective cover comprises a protective cover shell and a ventilation pipe positioned in the protective cover shell; exhaust holes are formed in the pipe wall of the ventilation pipe and the protective cover shell; the exhaust holes formed in the pipe wall of the ventilation pipe is distributed on a lower half part of pipe wall of the ventilation pipe; a welding gun gripper, a first control mechanism for controlling a distance between a welding gun and the protective cover and a second control mechanism for controlling the height of the protective cover are arranged on the protective cover shell. The ventilation pipe of the protective cover disclosed by the invention is only perforated on the part below the cross section level, so that the gas pressure in the pipe is increased when the same flow of the gas is input, the gas has relatively high flow velocity, the sprayed gas is preferably centralized in the direction that welding seams are protected, the protection efficiency is improved, the protective gas is saved, the gas is environment-friendly and economic, and progression of times is adapted.