Abstract: Arc assisted Activating TIG welding is a new welding process with high efficiency,which includes separated arc AA-TIG and coupled arc AA-TIG. In this paper,with stainless steel as the base metal,the effect of quantity of O₂ in the assisting arc on the structure and properties of the weld was investigated. The experimental results show that the weld structure consisted of mainly austenite with a small amount of ferrite distributing in the austenite boundaries,and the tensile strength of the weld was consistent. With the increase of the introduced quantity of O₂,the low-temperature impact toughness of the weld slightly decreased. The impact toughness of the weld dropped less in coupled arc AA-TIG welding than in separated arc AA-TIG welding. When the introduced quantity of O₂ was less than 2 L/min, the impact toughness of weld in coupling arc AA-TIG weld was even better than that in traditional TIG welding.