In this study, we investigated the effect of mixing α-Al2O3 and γ-Al2O3 with a Pt catalyst on CH4 selective catalytic reduction (SCR). Among the prepared catalysts, the Pt/α-Al2O3 catalyst was found to have the lowest catalytic activity, but the best adsorption characteristics for CH4, which was used as the reductant. In contrast, the Pt/γ-Al2O3 catalyst was found to exhibit relatively high catalytic activity and moderate adsorption characteristics. To simultaneously enhance the catalytic activity and CH4 adsorption characteristics, we developed a new catalyst, Pt/γ-Al2O3 + Pt/α-Al2O3, by mixing α-Al2O3 and γ-Al2O3 with a Pt catalyst. The catalytic activity test confirmed that mixing these catalysts led to enhanced catalytic activity.