Abstract: Lignocellulosic biomass is the most abundant renewable carbon resource on the planet,which has the potential to replace oil to produce clean fuels and chemicals. At present, the efficient uti⁃lization of lignin components is difficult, which is the key to realizing the utilization of all components ofbiomass. To achieve the high-value utilization of lignocellulosic components, this review investigatesthe separation mechanism based on the " lignin-first" strategy, compiles the research progress of reduc⁃tive catalytic fractionation, and explores the factors of yield and selectivity of phenolic monomers, de⁃gree of delignification and retention of carbohydrate pulp, analyzed the influence of biomass feedstock,solvent, acid and base additives, catalyst, and reactors on the " lignin-first" strategy. In addition, thisreview also proposes new design ideas for catalysts and reactors and the research direction of reductivecatalytic fractionation. The analysis shows that the yield of phenolic monomers decreases in the order ofhardwood→herbaceous crop→softwood. The alcohol-water two-phase system is favorable for the ex⁃traction and dissolution of lignin and hemicellulose as well as the retention of cellulose structure. Theaddition of acid not only improves the degree of delignification and monomer yield but also promotes thehydrolysis of hemicellulose. The semi/ full flow reactor effectively avoids the separation of catalysts andcarbohydrate pulp.