Abstract: The gas reduction in the circulating fluidized bed (CFB) boiler,mainly CO,plays an important role on the reduction of NO catalyzed by the massive ash in the furnace and cyclones. The kinetic study of NO-CO reaction was conducted experimentally and the influences of ash existence and composition on the reactions were highlighted. Five typical coals were selected and the corresponding ash was prepared on the specific conditions,and the compositions were measured by X-Ray Fluorescence (XRF) method. A small-scale fixed bed test rig was set up and the ratios of NO reduction through the bed were obtained in different temperatures and reactant concentrations. The kinetic parame- ters were fitted by the experimental results subsequently. Ordered by the catalytic activity on NO-CO reaction,the rank of main metallic components in the ash is Fe2 O3 >CaO / MgO>Al2 O3 >SiO2 . Among them,the effect of Fe2 O3 is signifi- cantly higher,and SiO2 / Al2 O3 can be treated as inert components. By using the least square method (LSM) in the da- ta processing,an index was introduced as γash based on the weighted sum of mass fractions of ash components,to make the correction of NO-CO kinetic formula in the Arrhenius form. The formula was validated by the experimental results of NO-CO reaction catalyzed by the ash prepared artificially.