In this paper, the 6A01-T5 aluminum alloy hollow extrusion profiles with lock bottom for high-speed trains was welded by oscillating fiber laser-CMT arc hybrid welding. With optimized welding parameters, joints with uniform surface formation and without defects were obtained. Furthermore, the porosity distribution characteristics, microstructure and mechanical properties of the joint were investigated.The experimental results show that the joint formed by the oscillating laser hybrid welding has excellent forming quality. The average porosity rate of cross-section and longitudinal section is 0.63% and 0.06%, respectively. The round porosities with regular shape and diameter less than 50.0 μm are dominant, and the technological porosities in the weld bead are obviously restrained, compared to the non-oscillating laser hybrid welding. The central microstructure of the weld bead is dendrites, and the secondary dendrite is obviously weakened along the weld centerline. The microhardness of the fusion zone and heat affected zone is lower than that of base metal, which means the two zones are the softening zone.The fatigue limit of the hybrid joints is 105.0 MPa and the average tensile strength of joints is 223.19 MPa, while the tensile strength is up to 84.22% of the base metal. The tensile fracture shows an obvious dimple shape, which is the typical characteristic of ductile fracture.