N/TiO2 photocatalyst was synthesized by modified sol–gel method and characterized by XRD, XPS and DRS. The photoactivity of N/TiO2 were evaluated by the degradation of 2-naphthalenesulfonate (2-NS) under different light sources. The results showed that nitrogen doping may cause band gap narrowing of TiO2, and therefore increase the photocatalytivity of N/TiO2 under visible-light. The average particle size of the N/TiO2 synthesized is about 10 nm, and the N/TiO2 contains 100% anatase phase of TiO2. The dopant is found mainly to be NOx and the doping concentration in NT is 1.30%. The NT shows very high efficiency for the catalysis of the degradation of 2-NS. The degradation efficiency of 2-NS using NT under visible light for 5 h is 47.29%, much higher than 2.5% of the pure TiO2.