Reactions of diesel soot and NOx with and without O2 were carried out over CuFe2O4 catalyst. The ignition temperature of soot with the NO+O2 feed was lower than that in O2 or NO but close to those in NO2 and NO2+O2, indicating the implication of NO2 especially in decreasing the ignition temperature. On the other hand, the reduction of NOx into N2 was enhanced by coexisting O2. Based on these results and mechanisms of O2-soot and NO-soot reactions, the possible reaction mechanism of the simultaneous NOx-soot removal with the NO+O2 feed has been proposed.