The utility model provides a downdraft radiant tube biomass gasification gasification furnace and system gas system, including downdraft radiant tube biomass gasification gasification furnace, gasification furnace's coal gas suction device is through the gas output pipe connection to being used for the grey gas separator with coal gas and ashes separation, ash gas separator passes through gas piping and connects the heat exchanger, the coal gas of heat exchanger after with cooling is inputed through gas piping and is carried out gas dust disposal in the sack cleaner, , saves the coal gas afterthe sack cleaner removes dust in carrying coal gas storage tank through the draught fan, the exit linkage steam conduit of heat exchanger, the steam conduit is connected to the steam distribution ware of setting in the furnace body, utilize the regenerative radiant tube combustor to carry out biomass gasification, it is high to synthesize the thermal efficiency, requirement to the material size is fairly loose, can continuous system gas.