N2O, as a green propellant alternative to N2H4, shows potential application in satellite propulsion system. The state of Ir species and the reaction behaviors on Ir/Al2O3 in the oxidative environment during N2O decomposition were identified here. Two types of Ir sites existed in this catalyst and affected the process of N2O decomposition. The strong Ir sites facilitated the dissociative adsorption of N2O to form N-2 and adsorbed O atoms with adsorption heat of as high as 281 kJ/mol, which promoted the desorption of adsorbed O atoms and favored the self-sustaining decomposition of N2O by raising the catalyst bed temperature. The other Ir sites interacted weakly with O atoms but facilitated their combination to form O-2. The Ir/Al2O3 catalyst then exhibited an excellent performance in initiating the decomposition of N2O at low temperature of 200 degrees C and good stability in 0.1 N microthruster for orbit adjustment and attitude control of satellite. (c) 2016 American Institute of Chemical Engineers AIChE J, 62: 3973-3981, 2016