The influences of CO/O-2 in N2O reduction by biomass char have been investigated in a fixed-bed system based on the test of homogeneous interactions between CO/O-2 and N2O. Results show that self-decomposition of N2O starts at about 1173 K. N2O reduction was greatly enhanced with an increase in the CO concentration but insensitive to O-2 addition. When biomass char is loaded, the starting temperature of N2O reduction is lowered to around 773 K. In addition, CO addition improves the interaction between N2O and biomass char until it reaches an optimal concentration (1%), beyond which the level of improvement will decrease. The apparent activation energy for the char N2O reaction decreases from 81 to 72 kJ mol(-1) when CO addition reaches 0.5%. Further, the addition of O-2 at a higher temperature greatly suppresses the reduction of N2O by biomass char, because of the vast consumption of biomass char by O-2. To minimize the effect of char consumption, a chemical sorption test was conducted at 673 K, and the results confirm that O-2 addition indeed inhibits the chemical sorption of N2O on the surface of biomass char.