CuO-Fe2O3 catalysts categorized by the thermal treatment were systematically investigated for ammonia oxidation to nitrogen. The activity results exhibited that the calcination temperature had a significant contribution to the difference of the catalytic performance. Lower calcination temperature (<= 500 degrees C) resulted in the excellent catalytic activity owing to the formation of large surface area, superior redox behavior and abundant surface oxygen species. On the contrary, the catalytic activity of catalysts declined with further raising the calcination temperature (>= 600 degrees C) due to the destroyed structure and acid sites. In addition to this, DRIFTS study revealed that the reaction of ammonia oxidation largely depended on the presence of surface active oxygen on the catalysts. In particular, fast ammonia activation was observed on CuO-Fe2O3-500 degrees C, which was reflected by the rapid formation of -NH2 and nitrate species on DRIFTS combining the XPS results. The intermediates -NH2 and NO of internal selective catalytic reduction (iSCR) predominantly accounted for the excellent catalytic activities.