Lignocellulose has garnered significant attention as a green carbon source, offering a sustainable alternative to fossil fuels in pursuit of carbon neutrality. Among its components, lignin stands out as a renewable aromatic polymer that can be converted into valuable chemicals. In this study, we designed a Ru/Mg(OH)₂ catalyst for self-supplied hydrogen induced reductive catalytic fractionation (SCF) of lignocellulose, eliminating the need for external H₂. This catalyst achieved a high yield of lignin-derived monomers (50.7 wt%) using water due to the synergistic effect between Ru and the Mg(OH)₂ support. Furthermore, model compound studies were conducted to elucidate the lignin depolymerization pathway during the SCF process. These findings of the self-supplied hydrogenolysis strategy for lignin valorization have the potential to inspire further advancements in sustainable biorefinery technologies.