Abstract: Calculations of reactions between biomass char and oxygen carriers CuO were conducted via the method of Gibbs free energy minimization. The effect of temperature, mass ration of oxygen carrier/biomass char and pressure on the gasification of biomass char was examined. The reactions were experimentally investigated using thermogravimetric analysis and scanning electron microscopy (SEM). The results show that when using CuO as oxygen carrier in chemical looping gasification (CLG) of biomass char, the conversion rate of biomass char is improved with increasing reaction temperature. The oxygen carrier CuO starts to sinter when the reaction temperature is above 750 ℃. The addition of oxygen carrier has the best enhancement on the CLG of biomass char with mass ratio of biomass char/CuO being 1:6. It is also found that the increase of reaction pressure would inhibit the CLG of biomass chars.