Abstract: Simultaneous catalytic removal of soot particulate and NO_x in the presence of excess oxygen was investigated over Nd₂O₃-based metal oxides by using temperature programmed reaction (TPR).The catalytic performance depended significantly on loaded metal oxides, in which the catalyst containing potassium oxide- and manganese oxide-supported neodymium oxide(K/Mn/Nd₂O₃) was the best catalyst in the study. As a result, the ignition temperature of soot was reduced from 500℃ to 330℃, and the conversion efficiency of NO_x to N₂ was increased to 75.4%. Potassium oxide promoted obviously the catalytic activities, especially in decreasing the ignition temperature of soot. The amount of potassium oxide had an optimum ［2 mmol•(g rare earth oxide)^-1］, and too much loading of potassium oxide might cause the covering of active sites of the rare earth oxide.