We reported metallic ruthenium (Ru) nanoparticles loaded on amino modified dendritic mesoporous silica microspheres (Ru/NH2‐DMSMs) for ammonia decomposition to hydrogen. The sizes of the loaded Ru nanoparticles on carrier are 2~3 nm, providing rich active sites for ammonia decomposition reaction. As a result, the obtained Ru/NH2‐DMSMs‐5.1 can afford almost ~100% ammonia decomposition at 550 °C, due to the unique mesoporous structure of DMSMs inhibiting the aggregation of active Ru nanoparticles and enhancing the mass transport of ammonia.