NOVELTY - A back-heating biomass pyrolysis gasification device has a feeding device (10) for charging biomass fuels, a biomass drying device (20), a biomass pyrolysis gasification device (30), a biological carbon discharging device (40), and a synthesis gas burning device (50). The back-heating device further comprises flue gas refluxing device, and Venturi negative pressure device.    USE - A back-heating biomass pyrolysis gasification device.    DETAILED DESCRIPTION - A back-heating biomass pyrolysis gasification device comprises a feeding device (10) used for charging biomass fuels. A biomass drying device (20) whose inlet is connected with the outlet of the feeding device and which is used for drying the biomass fuels. A biomass pyrolysis gasification device (30) whose inlet is connected with the outlet of the biomass drying device and which is used for carrying out pyrolysis gasification on the dried biomass fuels to generate synthesis gas. A biological carbon discharging device (40) whose inlet is connected with the outlet of the biomass pyrolysis gasification device and which is used for discharging biological carbon generated by the pyrolyzed and gasified biomass. A synthesis gas burning device (50) whose inlet is connected with the flue gas outlet of the biomass pyrolysis gasification device and which is used for burning the synthesis gas, generating high temperature flue gas and gradually converting heat in the high temperature flue gas to steams. A flue gas refluxing device whose inlet is connected with the outlet of the synthesis gas burning device, the biomass pyrolysis gasification device and biomass drying device and which is used for feeding back a part of high temperature flue gas generated by the synthesis gas burning device to the biomass pyrolysis gasification device and biomass drying device. A Venturi negative pressure device whose inlet is connected with the outlet of the flue gas refluxing device and which is used for discharging the flue gas of the flue gas refluxing device into a burning chamber of the synthesis gas burning device.    DESCRIPTION OF DRAWING(S) - The drawing shows a sectional view of the back-heating biomass pyrolysis gasification device.    Feeding device (10)    Biomass drying device (20)    Biomass pyrolysis gasification device (30)    Biological carbon discharging device (40)    Synthesis gas burning device (50)