The highly ordered Ni-P alloy nanotube and nanowire arrays with high aspect-ratio have been successfully synthesized inside porous anodic aluminum oxide (AAO) membranes by self-assembly electrode-position at different current densities. The as-synthesized Ni-P alloy arrays have the amorphous phase structure with nanograin of crystalline Ni. The length and outer diameter predominantly determined by the deposition time and pore diameter of the AAO membranes achieve 40 mu m and 200 nm, respectively. The formation of nanotubes or nanowires during electrodeposition mainly depends on the current densities, deposition time and phosphorous acid concentration in the electroplating bath. The magnetic properties of these nanostructure arrays have also been studied. From the hysteresis loops, it is obtained that the nanotube and nanowire arrays have anisotropy with the easy magnetization along the direction of the arrays. Moreover, as the soft magnetic materials, the nanotube array is better than nanowire array in magnetic performance of saturation magnetization. (C) 2010 Elsevier B.V. All rights reserved.