The invention provides an austenitic stainless steel argon tungsten-arc welding active agent and relates to the field of activators for welding. The active agent provided by the invention is composedof oxides and is poisonless and harmless. After the active agent is added, the quantity of metallic vapor generated on the surface of a molten pool is restrained, under the circumstance of little metal vapor, only metal within a small range near an anode spot rises, is gasified and ionized, thus an arc electric conduction channel is tightened, arc pressure is increased, flowing of metal liquid inthe molten pool is quickened, enlarged and deepened, fusion depth is increased substantially, and 16-mm single face welding and double face shaping can be achieved. In addition, SiO2 enables the content of Si in a weld joint to be increased slightly through metallurgic reaction, Si has a direct influence on a solidification mode, Si can increase w(Cr)eq / w(Ni)eq, the development of FA solidification mode is facilitated, the ferritiszation effect is facilitated, generation of a delta phase can be facilitated, the development of austenitic dendrites is hindered, and mechanical properties of a weld joint structure are improved.