Development of highly active catalyst for producing COX-free H-2 from ammonia decomposition is critical for the utilization of ammonia as H-2 carrier in proton exchange membrane fuel cell. Here, we present a deposition-precipitation (DP) method towards the synthesis of a highly active and stable mesoporous Ru/MgO catalyst for NH3 decomposition reaction. Nitrogen sorption measurements show that the deposition-precipitation method can introduce mesoporosity into the Ru/MgO-DP catalysts. Much enhanced Ru dispersion can be observed for the mesoporous Ru/MgO-DP catalysts in comparison with that of the Ru/MgO catalysts prepared by impregnation method due to the high surface area and plenty of mesopores of the Ru/MgO-DP catalysts. As a result, the mesoporous Ru/MgO-DP catalysts show significantly improved catalytic activity for NH3 decomposition. The activity of Ru/MgO-DP catalyst can be further remarkable enhanced with KOH, which can give comparable catalytic performance with that of the most efficient carbon nanotube supported Ru catalyst. (C) 2017 Elsevier B.V. All rights reserved.