In this study, laser-MIG hybrid welding and MIG welding were performed on aluminum-alloy crossbeam components of high-speed trains. Additionally, the weld formation as well as the microstructure and mechanical properties of the two welding methods were compared and investigated. The results show that both welding methods can achieve welds with good forming quality. Compared with MIG welding, laser-MIG hybrid welding offers a higher efficiency by approximately eight times while reducing the line energy by approximately 70%. The weld center of the two welding methods is a dendritic crystal. Compared with MIG welding, the laser-MIG hybrid welding features a columnar crystal in the fusion line at the weld side and the fusion zone is ambiguous. The hardness of the weld center resulting from laser-MIG hybrid welding is slightly higher than that from MIG welding. The lowest hardness achieved by laser-MIG hybrid welding is near the fusion line, whereas that achieved by MIG welding is in the weld area. The tensile strength of joints resulting from laser-MIG hybrid welding and MIG welding are 218.7 MPa and 177.0 MPa, respectively. The tensile specimens are fractured near the fusion line and weld zone, respectively, and both present the typical plastic fracture.