Highly ordered tungsten trioxide nanotube arrays were synthesized by the combination of (NH 4) 2WO 4 solution and anodic aluminum oxide(AAO) templating method. The morphology and the chemical composition of tungsten trioxide nanotube arrays were characterized by scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray photoelectron spectroscopy(XPS) and X-ray diffraction(XRD). The results show that the diameter of the tungsten trioxide nanotube arrays is about 165 nm and just equals to the diameter of pores of AAO template, which reveals that the diameter of the tungsten trioxide nanotube arrays is dependable on the size of the pores in the AAO template. The tungsten trioxide nanotubes are composed by tungsten trioxide nanoparticles formed by reaction (NH 4) 2WO 4550 ℃2NH 3↑+WO 3+H 2O↑ in the heating process.