A thin film TiO₂ in hierarchical nano-structure with high photocatalytic activities was synthesized in simple steps with ultrasonication. The crystal structure and morphology of the photocatalyst were investigated by X-ray diffraction (XRD) and high-resolution field emission scanning electron microscope (FE-SEM). In the present work, nanostructured TiO₂ was directly formed onto a Ti substrate via a solution approach. This nanostructured TiO₂ photocatalyst can be reused and will not generate secondary contamination to treated water. The photocatalytic activity of the synthesized TiO₂ photocatalyst was evaluated by the degradation of phenol under UVC irradiation in water and was compared with the general sol-gel derived TiO₂ films as well as a commercial DP-25 TiO₂ coating. It was found that the synthesized nanostructured TiO2has significantly high and stable photocatalytic activity.