Contraposing the welding defects of double-sided laser beam welded 6056/6156 aluminum alloys T-joints for the aircraft panels, systematic research on the repair welding process is carried out from the weld appearance, microstructure, and mechanical properties. The results show that double-sided repair welding with filler wire can eliminate the welding defects of the original joints and obtain good weld appearance, and the equiaxial crystal grain refinement is obvious. The dispersively distributed second phase particles in the heat affected zone are reduced, which causes the joints softened more significantly. The transverse tensile strength and axial tensile strength of the double-sided repair joints with filler wire are 323.9 MPa and 183.5 MPa, being 95.8% and 89.8% of the original joints, respectively. Axial tensile fracture surface appears mixed modes of brittle and ductile fracture, and the transverse tensile fracture surface appears brittle fracture characteristics.