Abstract: ER5356 welding wire was utilized for MIG/FSW composite welding to butt weld 3 mm-thick 7075 aluminum alloy plates, followed by T6 heat treatment(480 ℃/1 h +water quenching +120 ℃/24 h) for the welding joint. The microstructure and mechanical properties of the welding joint were analyzed using optical microscopy(OM), scanning electron microscope(SEM), energy dispersive spectrometer(EDS), room temperature tensile tests, and microhardness tests. The results show that after MIG/FSW composite welding, the weld microstructure exhibits small equiaxed crystals. The large,continuously distributed grain boundary precipitates transform into small, dispersed distributions due to stirring, resulting in increased microhardness. However, after FSW, a new heat-affected zone is generated in the region, which corresponds to the base material during MIG welding. Consequently, the overall strength of the composite welding joint does not exhibit significant improvement compared to the MIG-welded joint. After heat treatment, the majority of precipitates in the heat-affected zone dissolve into the matrix, achieving solid solution strengthening and aging strengthening. The problem of regional softening is improved, the tensile strength of the welding joint can reach 345 MPa and elongation after fracture is11.5%.