DCSP-TIG with activating flux is a new welding technology. The process was applied to joining 2219-T87 aluminum alloys.Pore-free seams with good weld appearance could be acquired in relatively low welding current. The activating flux without oxide played a key role,which could dissolve the oxide film on aluminum surface,and reduce or eliminate the pores in joint by combining with hydrogen in arc. Compared with the variable polarity plasma arc welding,DCSP-TIG with activating flux had better mechanical properties due to the pore-free and fine-grain microstructure in the fusion zone.