In this study, we investigated the effect of the CexZr1-xO2 (CZ) addition onto Ni/Al2O3 catalysts on the catalytic performance in methane steam reforming. In the reaction results, the CZ-added Ni/Al2O3 catalyst showed higher CH4 conversion and H2 yield under the same reaction conditions than Ni/Al2O3. From the characterization data, the two catalysts had similar support porosity and Ni dispersion, confirming that the two properties could not determine the catalytic performance. However, the oxygen vacancy over the CZ-added Ni/Al2O3 catalyst induced an efficient steam activation at low reaction temperatures, resulting in an increase in the catalytic activity and H2 yield.