Our studies on the selective catalytic reduction of NO (SCR-deNO) properties of M/gamma-Al2O3 (M = Mn, Co, Cu) nanocatalysts are presented. All catalysts were prepared by homogeneous deposition precipitation using urea as the precursor for the precipitating agent. The SCR activity followed the order Mn/gamma-Al2O3 > Cu/gamma-Al2O3 > Co/gamma-Al2O3. The nanocatalysts were characterized with respect to their texture (N-2-BET), particle size (TEM), reducibility (H-2-TPR), and acidity (NH3-TPD). The TEM analysis revealed that the metal species have superior dispersion with less agglomeration and sintering on gamma-Al2O3 support. The H-2-TPR results con firmed that the Mn/gamma-Al2O3 nanocatalyst contains various oxidation states of manganese, which is useful for the catalyst to maintain the DeNO activities. The NH3-TPD studies indicated that the addition of transition metal can significantly increase the surface acidity and Mn/gamma-Al2O3 showed the most adsorbed sites of NH3. Characterization results indicated that the acidity and the redox properties of the catalyst play important roles in the final catalytic activity in the SCR-NO process.