A Ti-based metal organic compound is taken as the precursor to be decomposed in NH3 flow at a certain temperature to prepare modified TiO2 with high photocatalytic activity under visible-light irradiation. The processes of doping and crystallization of TiO2 are conducted at the same time during the treatment in the NH3 flow. This approach could efficiently dope N into anatase TiO2 lattice. The prepared TiO2 also has well-defined mesoporosity with a BET area of 217 m(2)/g.