A composition of Cu/ZnO/Al2O3 catalysts prepared by the impregnation method was optimized for water gas shift reaction (WGSR) coupled with CO oxidation in the reformed gas. The optimum composition of the impregnated catalyst for high WGSR activity was 5 wt.% Cu/5 wt.% ZnO/Al2O3. The optimum loading amounts of Cu and ZnO in the impregnated catalyst were smaller than those in the coprecipitated catalyst. Its catalytic activity above 200degreesC was comparable to that of the conventional coprecipitated Cu/ZnO/Al2O3 catalyst. However, the activity of the impregnated Cu/ZnO/Al2O3 catalysts was significantly lowered at 150 degreesC, whereas no deactivation was observed for the coprecipitated catalyst at the same temperature. It was found that deactivation occurred over impregnated catalysts with H2O and/or O-2 in the reaction gas; it prevented CO adsorption on the surface.