Abstract: For TIG butt welding of 2219 aluminum alloy,the single-sided two-layer welding process and two-sided three-layer welding process were used to carry out comparative tests,and the shape and microstructures of the welded joints were analyzed. The results show that both methods can obtain well appearance of weld,and the mechanical properties meet the structural design requirements. Compared with the oneside two-layer welded joint,the average value of the tensile strength and elongation of the welded joint fabricated by the two-sided three-layer welding increases by 1. 7% and 33. 3%,respectively. The tensile strength is basically the same and the elongation is greatly improved. Compared to the single-sided two-layer welding,the back sealing of the two-sided three-layer welding increases the width of the back weld,the shape of the back fusion line and the angle between the back fuse line and the horizontal direction have changed. The microstructures of the welded joints of the two methods are distinct,and the microstructures of the same area are not much different. At the same position on the back of the weld,the hardness values of the two processes have the same trend,and the back sealing weld increases the width of the overage soften-ing zone,which makes the elongation of the welded joint increase.