MnOx supported on γ-Al2O3, TiO2, Y-ZrO2 and SiO2 was prepared by an impregnation and a depositionprecipitation method, and their catalytic activities for the low-temperature selective catalytic reduction (SCR) of NOx with NH3 in the presence of excess O2 were examined. The catalytic activity of the catalysts prepared by a depositionprecipitation method was higher than that of catalysts prepared by an impregnation method. The activity follows in the order: MnOx/TiO2.MnOx/γ-Al2O3>MnOx/SiO2>MnOx/Y-ZrO2. Supported MnOx catalysts prepared by a deposition-precipitation method appeared to have an amorphous manganese oxide phase and those prepared by an impregnation method exhibited a crystalline MnO2 phase, respectively. The addition of SO2 with H2O in the feeding gas slightly deactivates the SCR activity of MnOx/TiO2 catalysts.