The invention relates to the technical field of arc welding equipment, and discloses an argon tungsten-arc welding gun which comprises an upper gun body, a middle insulator and a lower gun body, the upper gun body, the middle insulator and the lower gun body are arranged in an upper-middle-lower mode to form the complete welding gun, and a chuck is fixedly installed in the middle of the lower gun body. The liquid cooling cavity is formed in the chuck, water cooling used for cooling the chuck directly acts on the tungsten electrode bar, compared with original indirect action, the tungsten electrode bar can be more effectively prevented from being ablated, meanwhile, the power control device is arranged in the liquid cooling cavity, two different flowing states of water flow during water supply and water cut-off are used as conditions, and the energy consumption is reduced. And once water cooling is stopped, power supply is stopped immediately, and the tungsten electrode bar does not work any more, so that the situation that the tungsten electrode bar is ablated before the welding gun is closed due to the lack of the cold area effect of water cooling during water supply is effectively prevented, the ablation and damage of the welding gun are avoided, and the replacement cost of the welding gun is effectively reduced.