The stability of the heterogeneous catalyst is critical to its working life. To improve the thermal stability of Pt/TiO2, an in-situ surface N-doping process was adopted by introducing a second nozzle above the spray pyrolysis flame, and in which method a high-temperature resistant catalyst was prepared and applied to the catalytic oxidation of CO. Moreover, the structure morphology, carrier phase composition, surface structure and species of the catalyst, the valence state of the loaded Pt particles and the surface element types were analyzed, which indicate that the nitrogen atoms are mainly present on the surface of the catalyst with interstitial doping in Ti-O-N and/or Ti-N-O structure. Besides, after calcination at 300 degrees C, 400 degrees C, 500 degrees C, and 600 degrees C, respectively, the particle size of these two catalysts and the phase transition of the TiO2 carrier were investigated. The results show that the N-doped Pt/TiO2 exhibited better stability, and its complete CO conversion temperature was controlled within 10 degrees C at 500 degrees C (Delta T-100 = 10 degrees C), which is more stable than 70 degrees C reduction of the pure Pt/TiO2 (Delta T-100 = 70 degrees C). This N-doped catalyst exhibits superior thermal stability in general, which is attributed to the formation of the stronger Pt-N bonds, resulting in a better resistance to sintering and a little phase transition during the calcination process.