The N-doped TiO2 nanotube arrays were prepared by electrochemical anodization and thermal annealing in ammonia flux. All the undoped and N-doped TiO2 nanotube arrays were pure anatase phase and the N-doped TiO2 shows obviously enhanced absorption intensity in the visible light region. The investigations on the low-frequency Eg anatase mode of Raman spectra verify that the crystallite size increases from 7.5 nm to 8.5 nm with the increase of the doped nitrogen temperature. The ratio of oxygen atoms to titanium atoms is 2.419 after titania being annealing in NH3 air stream. It could be concluded that the size effect and oxide vacancies introduced by nitrogen doping lead the great increase of UV-Vis absorption for N-doped TiO2 nanotubes.