Abstract: In order to further improve the quality of aluminum alloy welded joints, the alternating magnetic field-assisted cold metal transfer (CMT) technology was adopted for butt welding of the same 6061 aluminum alloy, and the influence of the magnetic field on the weld formation and microstructure properties of the joint was investigated. The results show that the application of an alternating magnetic field can ensure good weld formation, and it can significantly reduce the size of the joint porosity area and porosity. After the application of an alternating magnetic field, the grains at the center of the weld undergo obvious refinement, and the average hardness of the weld is 77.10 HV0.2, which is 21.63% higher than that of the weld without the application of magnetic field assistance. The elemental content of the weld is detected by an energy dispersive spectrometer (EDS), and it can be inferred that the Al-Si eutectic precipitation phase is mainly distributed along the α-Al grain boundaries. Under different magnetic field parameters, there is a softening zone in the heat-affected zone, and the fracture location is in this region. The fracture is ductile. Electrochemical corrosion is carried out in the weld, and the results of alternating current impedance and kinetic potential polarization curves show that the welds have better corrosion resistance after applying alternating magnetic field assistance.