Abstract: To further improve system flexibility and efficiency, a power factor correction circuit for a single-phase arc welding power source based on digital soft-switching technology was proposed. The overall hardware structure of the system, the topological principle of the selected soft-switching boost circuit, and the software design strategy were discussed. The power factor correction results of the soft switching were verified under two conditions: electronic load and tungsten inert gas (TIG) welding. Validated by the electrical signals of resonant capacitors and switches, it is confirmed that the circuit successfully achieves zero-current turn-on and zero-voltage turn-off. Through tests of power factor and efficiency under different power levels using an electronic load, results indicate that the power factor can reach above 0.985, and the overall efficiency is improved. Through TIG welding experiments under different welding currents, the electrical signals of the correction process were analyzed, verifying the effectiveness of the power factor correction for the single-phase arc welding power source.