The invention discloses a novel composite 
active agent for 
magnesium alloy active 
tungsten-insert-gas (A-TIG) 
arc welding, and belongs to an 
active agent welding technique. The novel composite 
active agent for 
magnesium alloy active 
tungsten-insert-gas 
arc welding provided by the invention is characterized in that the active agent is Cr2O3, and the weight proportion of the active agent is 65-70%; and a 
ceramic additive particle is SiC, and the weight proportion of the 
ceramic additive particle is 30%-35%. The novel composite active agent for 
magnesium alloy active 
tungsten-insert-gas 
arc welding is prepared through the following steps of: firstly 
grinding Cr2O3 active agent 
powder and the SiC 
ceramic particle, and mixing in proportion; then adding 
acetone into the mixture, so that the mixture becomes pasty; then 
coating the pasty active agent on the upper surface of a 
test sample uniformly by a flat 
brush, wherein the 
coating width is about 40mm, and the average density per 
square centimeter is 4-5mg; and carrying out tungsten-insert-gas (A-TIG) arc 
welding after the 
acetone is volatilized. Compared with a 
welding joint which is not coated with the active agent, the 
welding joint obtained through the welding technology has the advantages that the fusion depth is improved by 60%, an the tensile property is improved by 30%; and in addition, after the active agent is coated, 
crystal particles in the welding line are thinned obviously, and the difficulties that the fusion depth is shallow in the TIG arc welding, and the 
crystal particles of the welding line in the traditional active TIG arc welding are toughened seriously are solved.