Abstract: The local heating stress relief treatment is conducted on large thick Ti6321 titanium alloy welded joints by narrow gap vibration wire feeding welding, and the the effects of different local heating temperatures on residual stress, microstructure, and mechanical properties of titanium alloy welded joints are analyzed. The results show that for the welded joint without local heat treatment, the peak residual stresses in the direction perpendicular to the welding direction is 696.1MPa, and that parallel to the welding direction is 594.6 MPa. When the local heat treatment insulation time is 1 hour and the heating width is 240 mm, as the local heating temperature increases from 450 ℃ to 650 ℃, the peak residual stress of the joint continuously decreases. After the local heat treatment, the microstructure of the welded joint has no obvious change, with acicular α phase, intergranular β phase and intergranular α phase in the weld zone, and acicular structure in the heat affected zone.With the increase of heat treatment temperature, in the weld zone, the lamellar structure grows larger and its number increases, the width of the acicular α phase increases and its number decreases. In the heat affected zone, the width of the acicular α phase increases, the number and size of the primary α phase decreases. All the welded joints locally heat treated at three different temperatures can meet the use requirements, and the impact toughness of welded joint heat treated at 650 ℃ is the best.