The invention provides a hot wire welding device and belongs to the field of hot processing. A welding main arc is provided by a GMAW power supply, a parent material is connected with the negative electrode of the GMAW power supply, a welding gun is connected with the positive electrode of the GMAW power supply, and the parent material, the GMAW power supply and the welding gun form a current loop A; the current, voltage and dry elongation of the GMAW power supply can be freely adjusted according to experiment requirements, and the fusion depth and weld width of a weld pool can also be adjusted along with the current, the voltage and the dry elongation. Through alternate conduction of a power switch device in a hot wire current secondary inversion switching circuit, the power supply outputs low-frequency alternating current from a current output terminal, so that the current direction of a hot wire is switched back and forth, the hot wire effect on a welding wire is achieved through the switching, the welding efficiency is improved, and control over the swing of the main arc in the middle can also be achieved. A swing electric arc can also adjust the heat distribution of the electric arc, a heat affected zone can be adjusted, and the purpose that certain special alloy materials in the welding wire are not be damaged by electric arc overburning can be achieved. According to the device, energy input of the welding wire is reduced, and meanwhile, the swing electric arc plays an important role in improving the quality of the welding wire, so that the application range of the welding technology is improved.