The utility model discloses a water-cooled hot-wire tungsten electrode argon arc welding device for an austenitic stainless steel pipe. Welding efficiency is reduced if sensitization and tendency of producing thermal cracks are only controlled by reducing welding current and voltage and reducing welding heat input, so that the welding characteristic of high efficiency of mechanical hot-wire tungsten electrode argon arc welding cannot be brought into effect. The device comprises a welding gun (1), wherein a spray device with spray holes (3) is correspondingly arranged above a workpiece (2) which is connected with a revolving device; a spray head (4) of the spray device is connected with a water tank (6) through a water inlet pipe (5); the water inlet pipe is provided with a cooling water valve; and a dewatering disk (9) is arranged below the workpiece. The device is used for the argon arc welding of the austenitic stainless steel pipe.