The hydrothermal liquefaction of corn stalk under different atmospheres (N-2, H-2, and CO) was performed in a high pressure autoclave (500 mL) at 380 degrees C for 30 min, and the compositions of the liquefaction products were characterized by elemental analysis. It was found that the order of conversion of biomass, yield, and H/C ratio of liquid product follows: CO > H-2 > N-2; 10-13% oxygen is preserved in the liquid product and most of the oxygen in biomass is removed as CO2 and H2O; 64-79% and 24-31% of the original biomass' heating value is preserved in the liquid product and solid organic matter.