Abstract: Biomass can be converted into bio-oil by pyrolysis with high heating and cooling rates. Bio-oil is a crude oil which can be upgraded into high quality liquid fuels, for instance, it can be first gasified into syngas and then synthesized into methanol, dimethyl ether and so on. Considering bio-oil has high oxygen content, bio-oil gasification without any external supply of oxygen has been performed. The result shows that the mass conversion efficiencies of oxygen and hydrogen elements could be reached as high as 85%, but that of carbon is only 55%. Hence, the external oxygen supply should be needed to improve the mass conversion efficiency of bio-oil gasification.