Abstract: The conversion of biomass into hydrogen-rich gas provides a competitive means for producing clean energy and chemicals from renewable resources.Based on the principle of Gibbs free energy minimization, a new method was presented with better effectiveness and simplicity to be used for the prediction of chemical equilibrium composition of hydrogen production by biomass gasification in supercritical water(SCW).Applying this method to analyzing the process of glucose gasification in SCW, it was found that the product gas consisted primarily of hydrogen and carbon dioxide as well as a small amount of methane and carbon monoxide.The gas yield was strongly affected by reaction temperature and feedstock concentration and less affected by reaction pressure in the following range:temperature 623—1073 K,pressure 22.5—35 MPa,and concentration 0.1—0.8 mol•L^-1.The hydrogen production in product gas increased with the increase of temperature and decreased with the increase of concentration.