Abstract: 6063 aluminum alloy was welded by laser wire filling welding. After welding, the welded joints were treated by artificial aging, as well as solid solution and artificial aging. The microstructure and properties of 6063 aluminum alloy welded joints after post welding heat treatment were studied by means of optical microscope, scanning electron microscope and tensile test. The results show that the tensile strength of the untreated welded joint is 196 MPa, the internal structure of the weld is as cast, and Mg₂Si strengthening phase is dispersed. There are coarse columnar crystals growing into the weld near the fusion line, the internal of the weld is fine dendrite, and the center of the weld is equiaxed crystal. After aging treatment, the structural heterogeneity and the distribution of strengthening phase of the welded joint are improved, the tensile strength of welded joint is increased by 27 MPa. The tensile strength of welded joints treated with solid solution and aging treatment increased by 64 MPa. After solid solution and aging treatment, the microstructure of weld, fusion zone and heat affected zone are significantly refined. The fracture analysis shows that the welded joints are ductile brittle mixed fracture. The size of dimples on the fracture surface after aging treatment varies greatly, and the dimples are deeper. The fracture surface after solution and aging treatment shows more dimples, which are uniform, large and deep.