Using phenolic bio-oil as feedstock for sustainable production of alkane fuels is of great significance. Here, the hydrodeoxygenation of phenol and its derivatives has been systematically investigated in aqueous media with a dual-functional catalyst system consisting of water-soluble, ionic liquid-like copolymer A-stabilized nanocatalysts and the mineral acid H3PO4. The developed Ru/A-H3PO4 catalyst system achieved a complete phenol conversion with cyclohexane selectivity higher than 99 %, making it by far one of the most efficient systems for phenol hydrodeoxygenation. Mercury poisoning experiments revealed that the in situ generated Ru nanoparticles are true a heterogeneous catalyst for hydrogenation. The catalytic activity of metal site for phenol hydrodeoxygenation to cyclohexane decreased with the order of Ru>Rh>Pt≫Pd. Our findings also demonstrated the delicate balance between activity and stability of ionic liquid-like copolymer-stabilized nanocatalysts. The research highlights an efficient catalyst system of transforming phenols into alkanes.