Abstract: A novel variable polarity welding power with highfrequency pulse modulation is designed by means of superimposed circuit, which can produce arc characteristics of high-frequency pulse welding in variable polarity welding process.Based on mathematic model of arc pressure and process experiment, the high-frequency pulsed current can increase arc pressure in a large scale.In the same root-mean-square welding current, the arc pressure with high-frequency (5 kHz) pulsed current increase to 2 times of the normal tungsten inert-gas welding arc, and it helpful for increasing of arc stiffness and energy density.It also provides theoretical proof for further researches on the high-frequency pulse modulated variable polarity welding.