Abstract: AA-TIG welding is a new and efficient welding process before which pre-melting oxide layer was prepared on weld position by low current assisting arc with Ar+O₂ as shield gas.As a result, a deep and narrow weld bead can be obtained.In this experiment, through turning the assisting arc parameters to change the thickness of oxide layer, the influence of the thick of oxide layer on stainless steel weld formation was analyzed.The results show that the parameters of assisting arc have great effect on the thickness of oxide layer, the oxide layer becomes thicker when the oxygen gas flow rate or the heat input of assisting arc increase.And the thickness of oxide layer influences the weld depth/width ratio, the weld depth/width ratio climbs up at first and then declines with the increase of the thickness of oxide layer.