Abstract: Biomass gasification under O2-rich gas was carried out in a fluidized bed reactor. The effects of equivalence ratio and volume fraction of oxygen on gas composition, carbon conversion and low heating value (LHV) of fuel gas were investigated through a series of experiments. Equivalence ratio (ER) is closely related to the bed temperature changed by adjusting the feeding rate. When ER varied from 0.21 to 0.29, the gas compositions were changed. The volume fraction of hydrogen increases apparently when the volume fraction of reducing species, such as CO and CH4, decreases. The volume ratio of oxygen is a very important variable to the biomass gasification. It is concluded that increasing volume fraction of oxygen improves the volume fraction of H2 and contributes to adjust H2/CO ratio to an appropriate value. When the volume fraction of hydrogen is increased from 20% to 27.7%, H2/CO ratio is improved from 0.38 to 0.75, which is adequate to synthesize the liquid fuel.