Aqueous liquefaction of Cunninghamia lanceolata, Fraxinus mandshurica, Pinus massoniana Lamb. and Populus tomentosa Carr. was carried out in an autoclave in the reaction temperature range of 553. 15-633. 15 K, where both non-catalytic and catalytic liquefaction were performed. The experimental results show that the lignin content has a large effect on the yield of liquefaction products in the noncatalytic liquefaction. The addition of K2CO3 as a catalyst can significantly reduce the residue yield for all the woods tested, while its effect on the heavy oil yield becomes weaker with decreasing amounts of lignin. The present study shows that a heavy oil yield of 30% coupled with a residue yield of less than 10% can be obtained for all the wood samples tested in the catalytic liquefaction.