N-doped TiO2 nanotube (NT) arrays were prepared by anodization in electrolytes containing HF, 1-n-butyl-3-methyl-imidazolium tetrafluoroborate ([BMIM]BF4) ionic liquid and water. The ionic liquid, [BMIM]BF4, was used as the nitrogen source. The surface morphology and composition of samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR) and UV-Vis diffuse reflectance spectra (DRS). Photocatalytic activity of N-doped TiO2 NT arrays was investigated by degradation of methylene blue (MB) under spherical xenon lamp. The degradation rate of MB over N-doped TiO2 NT arrays was obviously higher than that over undoped TiO2 NT arrays. The results are caused by the increased oxygen vacancies and the decreased band gap.