Abstract: High-pressure liquefaction of a sawdust in syngas and hydrogen with tetralin as solvent was performed in an autoclave, and the effects of temperature, reaction time and initial reaction pressure on the sawdust high-pressure liquefaction were studied by testing the distribution and characteristic of liquefaction products. The effects of atmosphere on the products distribution and characteristic of sawdust liquefaction were also compared. The results show that the oil yield increases with increasing temperature, reaction time and pressure, while the effects of operating parameters on the oil yield are different: the temperature has a bigger effect than the reaction time and pressure. Under same conditions, the yield and characteristic of liquefaction products in hydrogen and syngas are almost the same, so it is possible to use syngas to replace hydrogen during biomass highpressure liquefaction. The optimal liquefaction conditions of the sawdust in tetralin at syngas atmosphere is 300℃, 2MPa pressure and reaction time of 30min with the conversion of 75.1% and the oil yield of 48.4%.