A series of anodic-alumina-supported silver catalysts (Ag/Al2O3) were synthesized to investigate the promotional effect of H-2 and electrical heating possibility on the selective catalytic reduction (SCR) of NO by C3H6. It was observed that the SCR activity of Ag/Al2O3 catalyst was greatly improved at low temperatures in the presence of H-2. Moreover, this promotional effect became more significant with increasing H-2 concentration. According to the results of the reaction without C3H6, H-2 did not significantly improve the activity; this indicates that the H-2 acted as a promoter but did not directly participate in NOx reduction. The results of NOx-TPD (Temperature Programmed Desorption) and NOx-H-2-TPR (Temperature Programmed Reduction) showed that the NOx adsorbed on the catalyst surface was quickly desorbed in the presence of H-2, while NOx desorption became faster by increasing the concentration of H-2 added to the flow as well as the Ag loadings. In the case of catalysts with low Ag loadings, nitrate poisoning was considered to be the main reason for low NOx conversion at low temperatures. On the other hand, in the case of the high Ag loadings, the scarcity of Ag-n(delta+) clusters was inferred to result in unfavorable SCR activity. Additionally, electrical heating tests on the SCR by C3H6 in the presence of Ag/Al2O3 catalysts showed excellent denitration activity and rapid reaction rate. On the basis of the electrical heating pattern, a new strategy for controlling NOx emission from diesel engines was formulated.