Abstract: For 2219 sheet aluminum alloy,TIG welding with different welding heat input was carried out. The mechanical properties,microstructure and fracture characteristics of the welded joint were analyzed. The results show that the average tensile strength of the joint of single pass welding is increased by 19. 6% and the elongation after fracture is basically the same. The joint of double weld is near the weld line,and the columnar dendrite is formed in the weld zone. Different shapes and irregular shapes,grain coarsening in the heat-affected zone,geometrical changes,and uneven microstructure. When the joint temperature increases,the grain coarsens and the strength decreases. The fracture shows a tear propagation along the grain boundary. The traces are partially"river pattern"; the joints of single pass are near the fusion line,the equiaxed crystals in the weld zone are more distributed,the structure is uniform,the grains are fine,and the joints are subjected to heating,rapid cooling and room temperature. The strengthening phase dissolves in the solid solution,the Cu atoms diffuse and aggregate,and the lattice distortion occurs,the crystal grains are refined,the strength is increased,and the fracture shows a typical shape of the fracture,and the shape of the dimple is obvious.