TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Process: Preferably, the biomass gasification process comprises: (a) drying and pyrolysing the biomass raw material under indirection heating function, and performing part gasification reaction with the primary gasification agent; (b) performing combustion and deoxidation reaction between the pyrolysed and partly gasified semicoke and the introduced secondary gasification agent; and (c) mixing the pyrolysed and partly gasified gaseous product and the gaseous product generated by the combustion and deoxidation reaction with the secondary gasification agent to perform imperfect combustion reaction, and implementing gas component reforming; where the equivalence ratio of the gasification agent in the whole gasification process is 0.2-0.35; and the ratio of primary gasification agent, secondary gasification agent, and third gasification agent is 0.0.8:2-3.5:0.7-1.5. Preferred Device: The used gasification furnace comprises a furnace body having a heat preservation layer; where the furnace body is equipped with a raw material feeding port, a product gas outlet, and a gasification agent entrance; the bottom of the furnace body is equipped with a fire grate and an ash discharge port; the furnace body is equipped with at least one pyrolysis cylinders made of high-temperature resistant material; the axis of each pyrolysis cylinder is vertical to section of the furnace body; an upper opening end of each pyrolysis cylinder is the raw material feeding port towering above an upper top end of the furnace body; a lower opening end of each pyrolysis cylinder is located at middle part in the furnace body; a gas reforming device is located between periphery of each pyrolysis cylinder and an inner wall of the furnace body; the gas reforming device separates the inner cavity of the furnace body into an upper part and a lower part; the upper part is a fuel gas chamber, and the lower part is the combustion chamber; the gasification agent entrance comprises a primary gasification agent entrance, a secondary gasification agent entrance, and a third gasification agent entrance; the primary gasification agent entrance and the raw material feeding port are same entrance; the secondary gasification agent entrance is located at bottom of the furnace body and communicated with the cavity at the lower part of the fire grate; and the third gasification agent entrance is connected with a gas separation ring having a nozzle in the combustion chamber.