Abstract: There is plentiful biomass, a renewable resource，in the world. Not only the problem of energy shortage can be solved，but also the amount of emission of carbon dioxide can be decreased by the effective utilization of biomass energy. Thermochemical conversion of biomass includes gasification, pyrolysis and liquefaction. Liquefaction has got more and more attention in recent years because of its advantages over other methods. In this paper, the progress in liquefaction of biomass is reviewed，including the effects of biomass type，solvent，catalyst，temperature, pressure，and reaction time on the yield and distribution of products. It is pointed out that the mainstream of liquefaction is to reduce the cost of liquefaction and decrease the oxygen content of bio–crude.