Supercritical water gasification (SCWG) with biomass is a combined thermal decomposition and hydrolysis process that converts biomass feedstock into hydrogen rich syngas. Renewable biomass as feedstock provides value for the sustainable development of this technology. This review discusses the relationship between cellulose, hemicellulose, lignin and hydrogen production; considers the effects of reaction temperature, pressure, reactant concentration and reaction residence time; and explores the advantages and drawbacks of different types of catalysts for enhanced SCWG hydrogen production process. The results show that temperature and catalyst have the greatest impact on SCWG. The other operating conditions are biomass type > pressure > reactant concentration > reaction residence time. However, the SCWG mechanism of real lignocellulosic biomass remains to be studied. The interaction relationship of three components is also unclear. In addition, the development of catalysts with high stability and performance is the top priority in the development of this technology.