NOVELTY - External-heating type biomass pyrolyzing gasification furnace comprises a bin (1), a combustion chamber, a trough (4) and a carbonized material cooling segment. The trough is equipped with the bin and the carbonized material cooling segment arranged below the trough is equipped with a carbonized material outlet. The bin is equipped with a biomass material inlet. The combustion chamber is equipped with an air inlet (5) and an exhaust gas outlet (6). The periphery of the trough is equipped with three independent circular combustion chambers in sequence from top to bottom.    USE - The furnace is useful for producing charcoal.    ADVANTAGE - The furnace produces charcoal with high yield and high quality; and occupies less space.    DETAILED DESCRIPTION - External-heating type biomass pyrolyzing gasification furnace comprises a bin (1), a combustion chamber, a trough (4) and a carbonized material cooling segment. The trough is equipped with the bin and the carbonized material cooling segment arranged below the trough is equipped with a carbonized material outlet. The bin is equipped with a biomass material inlet. The combustion chamber is equipped with an air inlet (5) and an exhaust gas outlet (6). The periphery of the trough is equipped with three independent circular combustion chambers in sequence from top to bottom. The outer wall of each combustion chamber is equipped with an air inlet and an exhaust gas outlet, while the inner wall is equipped with a gas overflow pipe, which is connected with the trough. An INDEPENDENT CLAIM is also included for preparing charcoal through continuous pyrolysis and gasification by using external-heating type biomass pyrolyzing gasification furnace, comprising (i) combusting the biomass material in the trough; (ii) introducing the generated pyrolysis gas into the three independent combustion chambers (I, II, III) through the gas overflow pipes for combusting with air; (iii) storing heat energy generated during combustion in the combustion chambers and transferring to the biomass material layer in the trough through the outer wall of the trough to maintain the pyrolysis temperature at 600-800 degrees C; and (iv) carrying out pyrolysis of biomass and cooling the carbonized material generated by pyrolysis reaction through the carbonized material cooling segment to obtain retort gas, and then discharging from the carbonized material outlet.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic representation of the external-heating type biomass pyrolyzing gasification furnace.    Bin (1)    Temperature control device (2)    Trough (4)    Air inlet (5)    Exhaust gas outlet (6)