This research proposes a method for fabricating CuO nanostructures by utilizing atomic diffusion including electromigration and stress migration. The samples are subjected to a current stressing under different combinations of current density and temperature. After current stressing, the samples are kept in atmosphere or in vacuum. The factors affecting the formation of CuO nanostructures, which are current density, temperature and storage environment, are studied. The current density can cause an effective Cu atomic diffusion and induce a gradient of atomic density along the direction of film thickness. However, a much higher current density induces a direct formation of mass CuO nanostructures on the Cu film due to Joule heating. In addition, CuO nanostructures are formed in the atmosphere more easily than in vacuum.