Abstract: Al MCM 41 and Cu Al MCM 41 were prepared by a modified hydrothermal method. The characterization using XRD, NMR and N 2 isothermal adsorption revealed that the structure of Al MCM 41 remained unchanged after the exchange of copper ion. The chemisorptive properties of Cu Al MCM 41 as well as its catalytic activity for the reaction of NO by C 3H 6 were investigated by TPD, in situ FTIR and temperature program reaction techniques. It was found that both propylene and NO could adsorb on the copper sites but the adsorption of propylene was more competitive. Thus, C 3H 6 not only played the role as reductant but also caused the inhibition of the adsorption of NO, which affected the conversion efficiency in turn.