NOVELTY - Preparing high-quality gas through biomass pyrolysis and decarbonisation, comprises: (i) carrying out biomass pyrolysis and catalytic pyrolysis of coke in a sleeve type pyrolysis device; (ii) passing the gas phase pyrolysis product into combustion chamber, heating, and cracking coke to obtain high-quality gas; (iii) pyrolysing the residual carbon and calcium carbonate, and decomposing the calcium carbonate by heat; and (iv) adding calcium oxide in a whirlwind separator, and adding gas solid into sleeve type pyrolysis device for pyrolysis, cracking coke, and recycling calcium oxide.    USE - The method is useful for preparing high-quality gas through biomass pyrolysis and decarbonisation.    ADVANTAGE - The method can be continuously carried out to obtain a multifunctional high-quality gas.    DETAILED DESCRIPTION - Preparing high-quality gas through biomass pyrolysis and decarbonisation, comprises: (i) introducing the biomass raw material and calcium oxide to a sleeve type pyrolysis device in the weight ratio of 1:0.2-1, and carrying out biomass pyrolysis, and catalytic pyrolysis of coke, and absorbing of carbon dioxide by calcium oxide; (ii) passing the gas phase pyrolysis product through pipelines into a combustion chamber, and heating directly at 900-1000 degrees C, and further cracking the coke to obtain high-quality gas; (iii) pyrolysing the residual carbon and calcium carbonate transferred from a conveying device to the combustion chamber, and decomposing the calcium carbonate by heat while burning; and (iv) introducing the reproduced calcium oxide in smoke while burning into a whirlwind separator, and adding gas solid separated by high temperature smoke into the interlayer of the sleeve type pyrolysis device for providing heat for pyrolysis and cracking coke, and then recycling the reproduced calcium oxide in the sleeve type pyrolysis device.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic representation of the device for preparing high-quality gas.