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.