Abstract: Based on SUS304 stainless steel, bead-on-plate experiments for both ordinary TIG welding and GPCA-TIG welding using O₂ as the outer gas were made to evaluate the oxygen content in the weld, micro-structure, the tensile properties and low temperature impact-toughness of the weld. The results show that, the weld micro-structure of GPCA-TIG welding mainly composites of austenite and ferrite. The morphology of ferrite is lacy and vermicular. Oxygen introduced as the outer gas makes the weld oxygen content increase. When the coupling degree is +2, the weld oxygen content is higher than that of coupling degree 0. The tensile strengths of the weld are all slight lower than those of the parent metal. The low temperature impact-toughness of the weld with coupling degree 0 is almost the same with that of TIG welding, while the low temperature impact-toughness value for coupling degree +2 is decreased and only reaches 85% of traditional TIG welding.