Abstract: With high-speed video system and memory realtime oscilloscope gathering welding current and arc shape information of variable polarity TIG (VPTIG)welding, effects of five parameters including welding current frequency, DCEP(direct current electrode positive)and DCEN (direct current electrode negative)time, DCEP and DCEN current amplitude on arc shape information and quality of weld were analyzed.The experiment showed that arc shape, arc welding pieces of power and heat input can be controlled by regulating the five parameters, which not only could control penetration, both sides of weld and liquidation district width on both sides of weld, but also reduced the loss of tungsten electrode.VPTIG welding craft for aluminum alloy with plate docking and low frequency impulse modulation were adopted, and the depth of fusion of single pass welding could reach 6 mm.Meanwhile, good appearance of weld and reliable quality of welded joint could be obtained