The photocatalytic activity was investigated by degradation of methylene blue aquoeus solution under visible light irradiation. The highest photocatalytic activity of nitrogen-doped TiO2 was gotten from the sample in which 0.5M guanidine carbonate was used as nitrogen source. Compared with pure TiO2 (from hydrothermal method) and P25-Degussa, the wavelength
range of nitrogen-doped TiO2 was shifted to visible light while pure TiO2 and P25-Degussa were showed in
ultraviolet region.