NO reduction to N-2 by C3H6 was investigated and compared over Cu-Al2O3 catalysts prepared by four different methods, namely, the conventional impregnation, co-precipitation, evaporation of a mixed aqueous solution, and xerogel methods. It was found that the catalyst preparation method as well as the Cu content exerts a significant influence on catalyst activity. For the catalysts prepared by the first three preparation methods, with the increase of Cu content from 5 to 15 wt%, the maximum NO reduction conversion decreased slightly, but the temperature for the maximum NO reduction also decreased. For the xerogel Cu-Al2O3, there was a significant decrease in NO reduction conversion with the increase of Cu content from 5 to 10 wt%. In the absence of water vapour, the Cu-Al2O3 catalyst prepared by the impregnation method exhibited the highest activity toward NO reduction. The purity of alumina support was found to be a crucial factor to the activity of the Cu-Al2O3 catalyst prepared by impregnation. Tn the presence of water vapour, a substantial decrease in NO conversion was observed for the Cu-Al2O3 catalysts prepared by the first three methods, especially fur the impregnated Cu-Al2O3 catalyst. In contrast, the presence of water vapour showed only a minor influence on the xerogel 5 wt% Cu-Al2O3 and it showed the highest activity for NO reduction in the presence of 20% water vapour. The xerogel 5 wt% Cu-Al2O3 catalyst was also found to be less affected by a 5 wt% sulfate deposition than the Cu-Al2O3 catalysts prepared by other methods.