A method for cooling and washing biomass syngas, the method including the following steps: 1) introducing biomass syngas having a temperature of between 1000 and 1100° C., a dust content of less than 20 g/Nm3, and a tar content of less than 3 g/Nm3 to a quench tower for condensing a slag; 2) introducing the biomass syngas after slag condensation to a waste heat boiler for recovering waste heat and condensing a heavy tar in the syngas; 3) introducing the biomass syngas from the waste heat boiler to a scrubbing-cooling tower for removing dust and decreasing a temperature of the syngas; and 4) introducing the biomass syngas after dust removal and temperature decrease from the scrubbing-cooling tower to an electro-precipitator for further removal of the dust and the tar.