Graphic carbon nitride prepared by the thermal decomposition of urea was used a catalyst support for the in situ immobilization of Ru nanoparticles (NPs) (Ru/g-C sub(3)N sub(4)). The catalytic property of Ru/g-C sub(3)N sub(4) was investigated in the hydrolysis of ammonia borane (AB) in an aqueous solution under mild conditions. Results show that the in situ generated Ru NPs are well dispersed on the surface of g-C sub(3)N sub(4) with a mean particle size of 2.8 nm. The catalytic performance for AB hydrolysis indicates that 3.28 wt% Ru/g-C sub(3)N sub(4) exhibits excellent catalytic activity with a high turnover frequency number of 313.0 mol H sub(2) (mol Ru.min) super(-1) at room temperature. This strategy may provide an eco-friendly catalytic system for developing a sustainable catalytic route to hydrogen production.