Abstract: The FEM were founded to simulate the tensile behavior for butt joint of 6063 aluminum alloy by TIG welding basedon the software of ABAQUS. The effects of HAZ width and thickness on deformation of joint were studied. Andthen the equivalent model of aluminum alloy TIG welded joint was established, which was validated by the thin-walled tube with weld seam. The results indicate that the stress states of welded joints with uneven mechanical properties are complicated compared to the base material. There is sudden change of thetriaxial stress between the base material and HAZ and between the weld metal and HAZ. At the same time, the position of the maximum triaxialstress is transferredfrom the boundary between the base material and HAZ to the boundary between the weld metal and HAZ with the increase of the width of HAZ. The triaxialstress of the welded joint depends on both the thickness of specimen and the geometrical dimension of welded joint. The equivalent model of aluminum alloy welded joint is 20 mm in width. The fine model and the equivalent model for aluminum alloy thin-walled tube with welding line are in goodagreement.