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Hydrothermal liquefaction (HTL) has recently received increasing attention and widely accepted to produce bio fuel due to its advantages in rapid reaction, using wet feed stocks with no lipid-content restriction.Compared with pyrolysis, hydrothermal liquefaction is the effective way to obtain upgraded physical and chemical properties of product. However, there is a big difference between liquefaction products and fossil fuels in oxygen content, moisture, heating value, total acid number (TAN) and viscosity. In the earlier research, most of them focus on changing conditions of liquefication but relatively no more research on material pretreatment of HTL. Therefore, pre-processing such as torrefaction, Chemical-Biological Pretreatment (CP-pretreatment) and mild pretreatment (such acid/alkaline pretreatment) used in HTL were reviewed in this paper. Moreover, by comparing the three pretreatment methods of biomass, bio-oil yield and the composition products at different liquefaction conditions were higher except torrefaction, but the reaction temperature was lower than that without being pretreated. In other words, pretreated raw material has highly improved in liquefaction conditions and product yields. Additionally, this review also provides a brief overview of barriers to achieve improvements in the future.