This article introduces a novel and valid process for preparing a high concentration substitutional N-doped TiO2 photocatalytic film, i.e. firstly the titanium substrate was plasma nitrided and then the N-doped TiO2 was synthesized on the surface of nitrided titanium by using micro-arc oxidation. Compared with the traditional thermal annealing, the present process provides a possibility to increase the nitrogen doping concentration up to 3.21 at.% and x to 0.11 in TiO2-xNx, which exhibits a significant red-shift in the band-gap transition, narrow band gap to 2.6 eV, higher photo-generated charge carrier density and improved photocatalytic property.