Highly ordered TiO2 nanotubes with different tube length were fabricated by anodization using C2H2O4 center dot 2H(2)O containing 0.5 wt.% NH4F (electrolyte A) and anhydrous dimethyl sulfoxide containing 1% HF (electrolyte B), respectively. Then cathodic reduction method was used to dope Pt in TiO2 nanotubes in chloroplatinic acid. The results indicated that cathodic reduction could efficiently platinize TiO2 nanotubes. Pt-doped TiO2 nanotubes with the longer length had the higher photocatalytic activity for degrading methyl orange under UV and visible irradiation. The longer tube length has a positive effect on the photocatalytic activity of Pt-doped TiO2 nanotubes. Besides, as the content of anatase further decreases, the photocatalytic activity drops gradually due to the reduction reaction in the surface area. (C) 2011 Elsevier B. V. All rights reserved.