A method for purifying biomass syngas, including: a) introducing syngas out of a gasifier, through a water-cooling flue to a water-cooling quench tower; b) introducing the syngas from the water-cooling quench tower to a waste heat boiler of a water-tube type and a waste heat boiler of a heat-tube type; c) washing the syngas from the waste heat boiler of the heat-tube type in a Venturi scrubber in the absence of a filler to remove dust; d) introducing the syngas from the Venturi scrubber to a wet electrical dust precipitator for conducting dust removal and tar mist removal; and e) extracting the syngas by a coal gas draft fan, and transporting the syngas to a wet gas tank for storage or to a downstream process for use.