NOVELTY - The process comprises contacting the biomass with oxygen and steam present in an amount effective to oxidize the biomass, treating the oxidized biomass with oxygen and steam in a first stage to heat the oxidized biomass at a temperature of 800-850 degrees C and in a second stage to heat the oxidized biomass at a temperature of 900-1000 degrees C higher than that of the first stage for producing synthesis gas, and recovering the synthesis gas. The oxygen is present in an amount effective to heat the biomass at a temperature of 600-725 degrees . The biomass is contacted with the oxygen at a weight ratio.    USE - The process is useful for producing synthesis gas such as carbon monoxide, carbon dioxide and hydrogen from biomass, where the synthesis gas is useful as a fuel gas in internal combustion engines, gas turbines and gas fired steam boiler plants, and to produce other desired materials such as methanol and ethanol.    ADVANTAGE - The process is capable of economically, rapidly and efficiently producing crude synthesis gas with high purity and without any impurities such as chlorine, fluorine and sulfur.    DETAILED DESCRIPTION - The process comprises contacting the biomass with oxygen and steam present in an amount effective to oxidize the biomass, treating the oxidized biomass with oxygen and steam in a first stage to heat the oxidized biomass at a temperature of 800-850 degrees C and in a second stage to heat the oxidized biomass at a temperature of 900-1000 degrees C higher than that of the first stage for producing synthesis gas, and recovering the synthesis gas. The oxygen is present in an amount effective to heat the biomass at a temperature of 600-725 degrees . The biomass is contacted with the oxygen at a weight ratio of oxygen to biomass of 0.25-0.30 of the stoichiometric weight ratio for complete combustion of the biomass. The biomass is contacted with the oxygen and the steam in a fluidized bed of particulate material. An INDEPENDENT CLAIM is included for a purified synthesis gas.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of a process for producing a synthesis gas.    Heat recovery unit (32)    Scrubber (40)    Separator (51)    Cooler (57)    Reboiler. (60)