Abstract: The bypass-current hot-wire plasma arc has been successfully applied to the welding and additive manufacturing of metallic materials with its high wire melting efficiency and good energy regulation mechanism. To deeply understand the thermal-force regulation of the plasma arc by the bypass-current, a research method combining numerical simulation and experimental investigation was adopted to quantitatively compare and analyze the physical behavior of plasma arc with different bypass-current. The results show that the bypass-current has a traction effect on the high-temperature plasma, and the traction tendency increases with the increase of the bypass-current; the bypass-current can significantly reduce the temperature of the bottom layer of the plasma arc, which can be reduced by a maximum of 793 K. In addition, the action area is also significantly reduced; under the action of the bypass-current, the gas-phase charged particles have a tendency to move to the wire end, and thus produces the hot wire effect, including resistance heat of the wire and shunt preheat, with the increase of the bypass-current; the bypass-current reduces the pressure at the bottom of the plasma arc by up to 16%.