Abstract: The low-temperature selective catalytic reduction (SCR) denitrification of a flue gas was carried out with Ce-MnO_x/ACFN. The denitrification efficiencies were studied by modifying the activated carbon fibers (ACF) and changing the Ce-MnO_x loading capacity, Ce/Mn molar ratio and operating conditions respectively. Ce-MnO_x/ACFN as a SCR denitrification catalyst has good activity at 70-110℃. The denitrification efficiency increases with rising temperature, and it improves obviously after the ACF is modified by nitric acid. With the increasing of Ce-MnO_x loading capacity and Ce/Mn molar ratio, the denitrification efficiency increases firstly and then decreases; but with the increasing of NH₃/NO molar ratio in the inlet flue gas, it increases firstly and then tends to be stable. When the volume fraction of vapor in the inlet flue gas is above 8% the denitrification efficiency decreases with the vapor volume fraction increasing.