The catalytic activity of Cu-Mn-CeOx/Al2O3/Al alumite catalyst in the selective catalytic reduction of nitric oxide by supplementation with propene (SCR-C3H6) was investigated at temperatures ranging from 473 to 773 K. Oxygen was found to have different effects on NO. removal at low and high temperatures. Introducing a small amount of oxygen could significantly promote the reduction of NOx at low temperatures. However, at high temperatures, the increase in oxygen substantially depressed NOx conversion. When oxygen exceeded the critical concentration point (S > 1.0, i.e. a net oxidizing condition), there was an optimal reaction temperature for maximal NOx conversion, which occurred at the temperature required for complete oxidation of propene. An increase in propene was always favorable in enhancing the reduction of NOx over the entire temperature range.