Ultrafine monodisperse Ru nanoparticles were synthesized by a facile strategy with nitrogen-doped porous hierarchically porous carbon material (HPCM) as support. The as-synthesized Ru nanoparticles with an average particle size of 1.41 nm were dispersed uniformly on the HPCM surface (Ru/HPCM). The Ru/HPCM catalyst exhibited a high turnover frequency of 440 min(-1) and could be reused for eight times in hydrogen generation from ammonia borane hydrolysis. The enhanced catalytic activity of Ru/HPCM could be attributed to the numerous active surface areas provided by ultrafine monodisperse Ru nanoparticles for the reaction. The confinement space of the support and the abundant surface functional groups increased the stability and reusability of the Ru/HPCM catalyst. This facile strategy for synthesis of ultrafine monodisperse metal nanoparticles with high catalytic activity and reusability shows potential for practical applications.