NOVELTY - Biomass gasification is performed by granulating biomass feedstock particle diameter of 25-35 mm and length of 50-100 mm into pyrolysis and gasification furnace, gasifying using mixture of oxygen and water vapor as gasification agent at 120-275 degrees C dried gasifier layer (101), 275-600 degrees C pyrolytic layer (102), and 800-1000 degrees C combustion layer (103) to form biomass crude gas, dust-removing by introducing biomass crude gas into cyclone dust collector, and feeding biomass crude gas into heat exchanger using decoking device to remove demineralized water trap tar and coke dust.    USE - Biomass gasification for chemically synthesizing syngas (claimed).    ADVANTAGE - High gasification and high carbon conversion rate are achieved, and process is energy saving and reduces emission.    DETAILED DESCRIPTION - Biomass gasification is performed by granulating biomass feedstock particle diameter of 25-35 mm and length of 50-100 mm into pyrolysis and gasification furnace, gasifying using mixture of oxygen and water vapor as gasification agent at 120-275 degrees C dried gasifier layer (101), 275-600 degrees C pyrolytic layer (102), and 800-1000 degrees C combustion layer (103) to form biomass crude gas, dust-removing by introducing biomass crude gas into cyclone dust collector, feeding biomass crude gas into heat exchanger using decoking device to remove demineralized water trap tar and coke dust to obtain biomass crude gas with tar content of less than or equal to 0.1 mg/Nm3, sending into washing tower to wash and remove free minor impurities to obtain biomass crude gas with ash content of less than or equal to 1 mg/Nm3, introducing washed crude gas into separator to remove free water, sending into air storage tank to dry by circulating semi-dry method, and performing desulfurization by using iron oxide as desulfurization sorbent, molybdenum cobalt as hydrogenation catalyst, and zinc oxide as desulfurization agent to obtain syngas with hydrogen sulfide content of less than or equal to 0.1 mg/Nm3.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic diagram of the 2-stage fixed bed gasification furnace.    Dried gasifier layer (101)    Pyrolytic layer (102)    Combustion layer (103)