N-doped TiO2 was synthesized by a facile so-gel method using urea as nitrogen resource. To seek the efficient N doping of TiO2 photocatalysts, non-thermal N-2 plasma was employed to treat N-doped TiO2 followed by calcination (N-TiO2 (NTP)) and compared with the conventional calcination (N-TiO2). The samples were evaluated under visible light irradiation for photocatalytic degradation of methyl orange (MO). To elucidate the plasma treatment effect, XRD, SEM, EDS, TEM, BET, UV-vis DRS, FT-IR and XPS techniques were used for catalyst characterization. N-TiO2 (NTP) possessed small particle size of 4.9 nm with better dispersion and narrow band gap of 1.6 eV. The visible-light photocatalytic activity of N-TiO2 (NTP) was much better than that of N-TiO2. And the photocatalytic degradation kinetics of the MO fitted with the Langmuir-Hinshelwood equation. The apparent reaction rate constant of N-TiO2 (NTP) was about 2.8 times as high as that of N-TiO2. The enhancement was ascribed to small particle size of N-doped TiO2 offering more surface active sites and high content of surface oxygen.