Abstract: A power factor correction circuit for single-phase arc welding power source using digital soft switching technology is proposed. The overall hardware structure of the system, the topology principle of the selected soft switch boost circuit, and the software design approach were discussed. And the power factor correction results of the soft switch were verified under two conditions: electronic load and TIG arc welding. By using resonant capacitors and electrical signals from switching tubes, it was confirmed that the circuit successfully achieved zero current conduction and zero voltage turn off; Through testing the power factor and efficiency of electronic loads at different powers, it has been confirmed that the power factor can reach 0.985 or above, and the overall efficiency has been improved; Through TIG arc welding experiments under different welding currents, the corrected electrical signals were analyzed to verify the effectiveness of power factor correction for single-phase arc welding power.