In the present work, the promotion effects by doping metals on K2Ti2O5 or by combining an additional NO oxidation catalyst are studied in detail for soot oxidation. The synthesized catalysts are characterized by X-ray diffraction. The promoting effects of NO and NO2 on soot oxidation were examined on both K2Ti2O5 and metal-doped K2Ti2O5 catalysts. With pure K2Ti2O5 catalyst, NO has a negligible promotion effect, because of the fact that K2Ti2O5, different from Pt catalysts, is unable to oxidize NO to NO2. Compared to the pure K2Ti2O5 catalyst, all the doped metals somehow enhance soot oxidation by decreasing the peak temperature (T-p). The activity follows the order of Pt/K2Ti2O5 (324 degrees C) > Co/K2Ti2O5 (331 degrees C) = Cu/K2Ti2O5 (331 degrees C) > Ce/K2Ti2O5 (335 degrees C) > K2Ti2O5 (352 degrees C). With NO2, soot starts to be oxidized at temperatures as low as 250 degrees C, even with pure K2Ti2O5. When K2Ti2O5 is combined with a NO oxidation catalyst (Co/K2Ti2O5), both the starting temperature (T-s) and T-p were greatly decreased, from 295 degrees C to 240 degrees C and from 352 degrees C to 326 degrees C, respectively. Therefore, the combination of K2Ti2O5 with a NO oxidation catalyst can enhance the soot oxidation activity significantly.