Ultrafine, highly dispersed Pt clusters were immobilized onto the Co nanoparticle surfaces by one-step pyrolysis of the precursor Pt(Ⅱ)-encapsulating Co-MOF-74. Owing to the small size effects of Pt clusters as well as the strongly enhanced synergistic interactions between Pt and Co atoms, the obtained Pt-on-Co/C400 catalysts exhibited excellent catalytic activity toward the hydrolysis of ammonia borane with an extremely high turnover frequency (TOF) value of 3 022 min^-1 at 303 K. Durability test indicated that the obtained Pt-on-Co/C400 catalysts possessed high catalytic stability, and there were no changes in the catalyst structures and catalytic activities after 10 cycles.