Abstract: High density,well ordered,vertically aligned and uniform titanium oxide nanotube arrays were fabricated on the surface of pure titanium sheet by direct electrochemical anodic oxidation with 0.5% HF and 0.5% HF+1 mol/L (NH₄)H₂PO₄ as the supporting electrolyte at 20 V.XRD and SEM techniques were used to characterize titanium oxide nanotube arrays.The XRD result shows that TiO₂ showed the anatase phase after having been annealed for 1 hour under 400℃.SEM shows the length of nanotubes did not increase after reaction for 20 mins in an electrolyte solution of 0.5% HF.But in an electrolyte solution of 0.5% HF+1 mol/L (NH₄)H₂PO₄,at 20 V after reaction for 15 h,the average diameter of nanotubes is about 70~90 nm,and the length of nanotubes is about 2.2 μm.Photo-electrochemical character curves were tested in an electrolyte solution of 1 mol/L KOH under the irradiation of a high-voltage mercury lamp,photocurrent is about 3.5 mA/cm² for nanotubes with a length of 2.2 μm.With TiO₂ nanotubes of 2.2 μm in length as anode,under illuminating of a high-voltage mercury lamp at 0.45 V bias potential,after 4 h,the COD degradation degree of Methylene Blue electrolyte (10 mg/L) is about 93%.