Novel Fe-Mn mixed-oxide catalysts were prepared for the low-temperature selective catalytic reduction (SCR) of NOx with ammonia in the presence of excess oxygen. It was found that Fe(0.4)-MnOx catalyst showed the highest activity, yielding 98.8% NOx conversion and 100% selectivity of N-2 at 120 degrees C at a space velocity of 30 000 h(-1). XRD results suggested that a new crystal phase of Fe3Mn3O8 was formed in the Fe-MnOx catalysts. TPR and Raman data showed that there was a strong interaction between the iron oxide and manganese oxide, which is responsible for the formation of the active center-Fe3Mn3O8. Intensive analysis of fresh, used, and regenerated catalysts by XPS revealed that electron transfer between Fen+ and Mnn+ ions in Fe3Mn3O8 may account for the long lifetime of the Fe (0.4)-MnOx catalyst. In addition, the SCR activity was suppressed a little in the presence of SO2 and H2O, but it was reversible after their removal.