The invention relates to an argon tungsten-arc welding gun and discloses a GTAW welding gun capable of strongly cooling a tungsten electrode by using dry ice. The GTAW welding gun comprises a gun bodyand a tungsten electrode seat which are integrally formed, wherein a tail cover equipped with a gas outlet hole is connected with the top of the gun body; an inner sleeve is arranged inside the gun body; a gas exhaust channel positioned at the upper part of the inner sleeve is connected to the gas outlet hole; blanking holes are formed in the lower part, designed to be of an inverted funnel-shaped structure, of the inner sleeve; a welding gun inner cavity positioned between the gun body and the inner sleeve is filled with solid dry ice; an inward-sunken conical top is arranged at the top of the tungsten electrode seat; a reaction chamber used for sublimation of the solid dry ice is formed between the inward-sunken conical top and the inverted funnel-shaped structure; a gas hood is arranged outside the tungsten electrode seat; a stilling chamber is formed between the gas hood and the tungsten electrode seat; a first gas inlet pipe and a second gas inlet pipe are symmetrically mounted on two sides of the gas hood; and a tungsten electrode and a tungsten electrode copper sleeve are mounted at the bottom end of the tungsten electrode seat. By adoption of the GTAW welding gun disclosedby the invention, the gun body of the GTAW welding gun, especially the tungsten electrode mounted at the head of the GTAW welding gun, can be strongly cooled; the root of an electric arc can be compressed within a wide electric current range; the constraint effect of the electric arc can be increased; the penetrating capability of the electric arc can be enhanced; and finally, the welding efficiency can be improved.