Using metatitanic acid and melamine as raw materials, C-N modified TiO2 photocatalyst were prepared by calcination annealing at 700 ℃ in air atmosphere. The samples before and after modification were characterized by XRD, FT-IR, XPS, SEM, UV-Vis, BET, etc. The results show that the modified material is a material of porous anatase crystal TiO2 having a large specific surface area. Part of O in the TiO2 lattice is replaced by N, amide compounds are adsorbed on the surface. Compared with pure TiO2, the catalytic oxidation efficiency of NO by C-N/TiO2 is greatly improved. The catalytic oxidation rate of NO by C-N/TiO2-2 reaches 69%.