The TiO2 nanotube array thin films were fabricated on pure Ti plates by anodization process and annealed at 450oC, 500oC and 550oC for 30 minutes, respectively. The methylene blue (MB) degradation test was further conducted to evaluate the effects of annealing on the photocatalytic ability of TiO2 nanotube array. It was observed that better photocatalytic ability was found for the thin film annealed at 450oC, which was mainly the anatase phase. On the other hand, the anatase/rutile mixed phases were discovered on thin films annealed at 500oC and 550oC, respectively. In this work, the photocatalytic ability of TiO2 nanotube array with mixed anatase/rutile phases was not comparable to that reported in literature. It was suggested that the MB degradation ability was not only related to the crystallinity structure, but also strongly influenced by the surface characteristics of TiO2 nanotube array thin film.