Abstract: A novel ultrafast-convert complex ultrasonic pulse square wave variable polarity arc welding technology for aluminum alloy is developed.With X-ray inspection, weld tensile tests and SEM, the plain butt welds characteristics and mechanical properties of 5A06, 2A14 and 2219 alloys are tested.The experimental results show that with the complex pulse square wave variable polarity TIG arc welding technology, the appearance of aluminum alloy welds is fine, welding quality is satisfying with no blowholes and cracks.Tensile properties of aluminum alloy joints are improved obviously.