Abstract: The technique of variable polarity plasma arc welding(VPPAW) is analyzed in terms of its development history. The application of VPPAW for materials and structures of China's new type large-size spacecraft is discussed with special emphasis on the engineering challenges, and then the countermeasures are proposed. Studies and tests show that VPPAW is one of the best processing schemes for the welding of medium-thick aluminum alloy structures. The application prospects of this technique are evaluated.