Fe–Ce–Mn/ZSM-5 catalysts were prepared and performance of catalysts in NO selective catalytic reduction by NH 3 was tested in the temperature range of 100–500 °C. NO conversion reached 96.6% and 98.1% at 200 °C and 300 °C respectively at a GHSV of 30,000 h −1. In situ diffuse reflectance infrared transform spectroscopy (DRIFTS) study was carried out for revealing the reaction mechanism. Two possible reaction pathways were proposed. One was that NO 2 could react with NH 4 + on Bronsted acid sites and the formed NO 2[NH 4 +] 2 would react with NO, producing N 2 and H 2O. Another way was that NH 3 was adsorbed and then reacted with NO or HNO 2. Possible intermediate NH 4NO 2 and NH 2NO were unstable and would decompose into N 2 and H 2O. The addition of Mn in Fe–Ce–Mn/ZSM-5 catalysts could contribute to provide more Bronsted acid sites which was beneficial for the adsorption of NH 3. The addition of both Fe and Ce could obviously increase the conversion of NO to NO 2. Introduction of Fe increased the oxidation of NH 3 slightly and the addition of Ce increased the oxidation of NH 3 significantly. The combination of manganese, iron and cerium could significantly enhance the low temperature SCR activity.