Abstract: The factors which affect the cleaning action and electrode loss in TIG welding of aluminium alloys using variable palarity power are studied.The process experiment shows that because more welding parameters can be adjusted,the arc shape can be efficiently controlled. By increasing the current value and shortening the time of half cycle in wihch the tungsten polarity is positive, we can change the arc shape from diffusion to focus,and make welding process close to DCEN welding. In this condition,the basic requirement of the cleaning actiou is satisfied,and the loss of tungsten is reduced.By flexibly controlling the weld formation, we can get a satisfied result.