Abstract: The microstructure and mechanical properties of 2219 aluminum alloys welded joints of helium shielded TIG welding and argon shielded TIG welding were investigated. The results show that, the width of the weld bead, the concavity and the width of heat affected zone in helium shielded TIG welding are smaller than those in argon shielded TIG welding. The microstructure and second-phase of them are similar. The grains in weld area are isometric. In heat affected zone, grain are coarse stripes, and there are the α aluminum substrate, the inter-metallic compound Al₂Cu and some eutectic structure. The amount of the second-phase particles in weld zone is larger than that in heat affected zone. The tensile strength of the welded joints are similar, and the fracture modes are both ductile fracture. The elongation and hardness of the welded joint of helium shielded TIG welding are larger.