NOVELTY - Purification of biomass flash pyrolysis tail gas involves crushing biomass raw material, subjecting obtained particles to pyrolysis reaction, performing gas-solid separation of obtained pyrolysis gas to separate pyrolytic carbon, condensing carbon-removed high-temperature pyrolysis gas, performing pyrolysis of obtained tail gas, decoking, removing impurity, subjecting obtained non-condensable gas to gas-liquid separation and outletting obtained purified pyrolysis tail gas as fuel gas. The dew point of water in the pyrolysis tail gas is -8 degrees C or less.    USE - Purification of biomass flash pyrolysis tail gas (claimed).    ADVANTAGE - The purifying device purifies biomass flash pyrolysis tail gas, with reduced energy consumption and reduced generation of secondary pollution by wastewater generated during wet-method decoking.    DETAILED DESCRIPTION - Purification of biomass flash pyrolysis tail gas involves crushing biomass raw material into particles having particle diameter of less than 2 mm, subjecting obtained particles to pyrolysis reaction at 450-600 degrees C, reacting for 0.5-2.5 seconds, performing gas-solid separation of obtained high-temperature pyrolysis gas to separate pyrolytic carbon, condensing carbon-removed high-temperature pyrolysis gas which is condensable gas into liquid bio-oil, collecting, performing pyrolysis of obtained tail gas at 35-60 degrees C, decoking obtained non-condensable gas, such that purified pyrolysis tar content in tail gas is 40 mg/Nm3 or more, removing impurity from decoked obtained non-condensable gas, such that tar content in pyrolysis tail gas is 15 mg/Nm3 or more, subjecting obtained non-condensable gas to gas-liquid separation to remove water content in pyrolysis tail gas, and outletting obtained purified pyrolysis tail gas as fuel gas. The dew point of water in the pyrolysis tail gas is -8 degrees C or less. An INDEPENDENT CLAIM is included for biomass flash pyrolysis tail gas purifying device, which has a pyrolysis reactor, feeding port, gas outlet, gas-solid separator provided with dust outlet, and adsorption tower.