The invention discloses an improved welding gun. The improved welding gun comprises a conducting rod body, a wear-resisting guide pipe arranged in the conducting rod body, a water cooling jacket fastened to the exterior of the conducting rod body, and a nut which is arranged at one end of the conducting rod body in a sleeving mode and can slide in the axis direction of the conducting rod body. A gas input channel and a powder input channel are axially formed in the water cooling jacket. According to the improved welding gun, electrical conductivity is effectively improved through the water cooling jacket, and the problems that as a conducting nozzle overheats, thread loosen, resistance is increased, and welding current and voltage are not stable are solved; the problems that as the conducting nozzle overheats, wear resistance is substantially reduced, a conducting nozzle hole is likely to become large and form an irregular circular hole, the arc center floats, and instability of the welding current and voltage is directly caused are solved, and the defect that various uncertainties exist in the welding surface is overcome. The service life of the conducting nozzle is prolonged, and splashing of a gun nozzle is reduced.