Abstract: Solvent liquefaction was an effective process which could utilize biomass raw materials efficiently and comprehensively. Compared with water as a single solvent, the mixed solvent system could reduce the reaction temperature and pressure, improve the conversion of biomass, reduce the oxygen content in bio-oil, and increase the yield of the target product. This paper reviewed the common water mixed solvent systems in recent years, including the role of alcohol-water cosolvent, polar aprotic solvent-water system and ionic liquid-water system in the degradation process of lignocellulosic biomass, especially the application characteristics of ethanol-water cosolvent, tetrahydrofuran (THF)-water cosolvent and γ-valerolactone (GVL)-water cosolvent in biomass liquefaction. This paper also gave the shortage and suggestions of these solvents in biomass liquefaction field. Finally, based on the consideration of the economic value, recovery and safety performance of the solvent itself, it is pointed out that the development of low-cost, environment-friendly and sustainable liquefying solvents would be the key development direction in the future.