Abstract: The mechanism of the effect of additional electric field on welding penetration depth in laser-TIG hybrid welding was analyzed by comparing with electric field effect on single laser welding and single TIG welding.Meanwhile, the mechanism is verified by the investigation on the effect of electric field at different laser powers and TIG welding currents.Results show that the electric field has influence on the weld penetration depth of laser-TIG welding by controlling the motion of the charges in the plasma in the laser keyhole.The penetration depth can be enhanced when the electrons are forced to move to the bottom of the laser keyhole.The higher laser poweris, the more obvious the enhancing effect of electric fieldis.When the TIG current increases, the effect of electric field is depressed.