Ammonia borane (AB) hydrolysis is a promising strategy for the development of hydrogen energy, and ultrafine metal nanoparticles (NPs) are attractive catalysts owing to their abundant active sites. In this work, porous graphitic carbon nitride (CN) are doped with reduced graphene oxide (rGO) and used as supports to evenly confine ultrafine Ru NPs with an adsorption-chemical reduction method. The results show that the different assembly methods and compositions affect the geometric and electronic characteristics of the composites, thus affecting the catalytic behavior in AB hydrolysis. Also, the effects of different Ru loadings and NaOH dosages are researched to improve the hydrolysis efficiency. Specifically, the optimal Ru/CN-rGO catalysts display exciting catalytic performance due to the proper porous structure, N, O co-doping and highly dispersed ultrafine Ru NPs. The corresponding turnover frequency (887.2 min^-1) in the presence of NaOH (1.00 mol L^-1) and the apparent activation energy (21.7 kJ mol^-1) are superior to many previous results. The facile fabrication strategy and robust performance attest to a promising potential for Ru/CN-rGO in the fields of hydrogen energy.