The hot-wire TIG welding equipment was built based on the heat-conduction method. The temperature-controlling model was developed and verified within a certain temperature range. The results showed that the wire temperature could be maintained at 220±5°C. The comparing experiments between the hot-wire TIG with a temperature of 220 °C and ordinary TIG were conducted. The results showed that the hot-wire TIG based on the heat-conduction method could improve the appearance and the feeding speed. When the appearance was similar, the efficiency of hot-wire TIG in root welding was doubled compared with that of the ordinary TIG. The efficiency of hot-wire TIG in cap welding was tripled compared with that of the ordinary TIG. Moreover, the microstructure of welding seam of the hot-wire TIG welding was finer than that of the ordinary TIG welding. The hardness of welding seam of the hot-wire TIG welding was harder than that of the ordinary TIG welding slightly. Good mechanical properties of the two joints have been indicated. The fracture was located in the ASTM A106 base metal.