[Ni80Fe20/Cu]15 multilayers were fabricated by dc-magnetron sputtering and annealed at 150, 250 and 350℃, respectively. The structures were investigated by low-angle and high-angle X-ray diffraction. It was found that, as the annealing temperature increases, the [111] preferred orientation of superlattices is improved slightly, while the superlattice period, interplane distance, average multilayer coherence length decrease. The interfacial roughness increases with the increase of annealing temperature and/or annealing time, this can be attributed to the Ni80Fe20 and Cu sublayers has been revealed by simulation of high-angle X-ray diffraction, and its thickness increases as the annealing temperature of annealing time increases. The simulation results furthermore showed that the interplane distances of the Ni80Fe20 layer keeps constant, and that the Cu layer decreases slightly as the annealing temperature increases.