Nitrogen-doped TiO2 nanomaterial attracts enormous attention due to its excellent visible photocatalytic activity. A simple annealing method assisted by adjusting gas composition to control the positions of nitrogen dopants in TiO2 lattice is presented. The nitrogen doping sites are confirmed by XPS. The photodegradation results of gaseous benzene under visible light illumination reveal that photocatalytic activity in as-prepared samples containing the substitutional nitrogen species is higher than that in samples containing interstitial nitrogen species. The improvement of photocatalytic performance is ascribed to the increased amounts of surface hydroxyl group in N-TiO2 samples. The efficient separation of electron-hole pairs was also responsible for the enhanced photocatalytic activity. In addition, an important conclusion is pointed out: the presence of oxygen during annealing process has an important effect on the formation of interstitial nitrogen dopants. The present work is believed to have guiding significance for preparing nitrogen-doped TiO2 with high photo catalytic activity. (C) 2014 Elsevier B.V. All rights reserved.