Abstract: A series of iron-cerium mixed oxide catalysts modified titanium, zirconium, tungsten and molybdenum were prepared by co-precipitation. The selective catalytic reduction of NO_x with NH₃(NH₃-SCR) activity of the catalysts were carried out in a fixed-bed quartz tube reactor. The research results indicated that the addition of tungsten and molybdenum could increase the high-temperature NH₃-SCR activity of the iron-cerium mixed oxide catalysts, but decreased its low-temperature NH₃-SCR activity. Titanium could improve the NH₃-SCR activity of the iron-cerium mixed oxide catalyst within the range of reaction temperature, especially at low-temperature. Titanium was the most suitable assistant. When increasing the molar fraction of titanium from 0.10 to 0.40, the low-temperature NH₃-SCR activity of iron-cerium-titanium mixed oxide catalysts firstly increased and then decreased while the high-temperature activity gradually increased to 100%, and the optimum molar fraction of titanium was 0.15. The results of X-ray diffraction(XRD) and N₂ adsorption isotherms showed that the addition of titanium could optimize the pore structure of iron-cerium mixed oxide catalyst, and increased the BET surface and the pore volume of the iron-cerium mixed oxide catalyst, meanwhile refined its pore size. At the some cases, titanium could react with iron oxide and cerium oxide within the iron-cerium mixed oxide catalyst to form the solid solution. Therefore, the addition of titanium could enhance the NH₃-SCR activity of iron-cerium mixed oxide catalyst. Under the condition of the test, more than 90% of NO_x conversion could be achieved over Fe_0.8Ce_0.05Ti_0.15O_z catalyst at the temperature range of 150～400℃.