Abstract: The double-sided friction stir welding was performed on 7N01 aluminum alloy sheet, in the mode of front side and back side welding for one pass each. The microstructure, hardness distribution, tensile properties and stress corrosion susceptibility of the joint were studied. The results show that the FSW joint was well formed. The weld nugget zone had a uniform and fine equiaxed crystal structure and the grains of the weld nugget zone at junction of weld beads were smaller than other weld nugget zones due to secondary thermo-mechanical couple effects. The grains in the thermal mechanically affected zone underwent shear deformation and showed a strip shape. The grains of the heat affected zone showed an original lath shape. The hardness decreased gradually from the weld nugget zone to base metal, and the hardness of the weld nugget zone at junction of weld beads was higher than that of other weld nugget zones. FSW joints fractured in the heat affected zone in air and 3.5wt% NaCl solution, indicating the heat affected zone was the weakest. The tensile properties of the joint were lower than those of the base metal, and the stress corrosion susceptibility was higher.