The invention relates to a draught fan filtering device. The draught fan filtering device comprises an air bellow and a connecting pipe. An air inlet is formed in the bottom of the air bellow, an air outlet is formed in the side face of the top of the air bellow, the air outlet is connected with the connecting pipe, a filtering device is arranged in the air bellow, impellers are arranged at the upper end and the lower end of the filtering device, and an adsorption device is arranged between the filtering device and each impeller. The draught fan filtering device has the advantages that the gas advancing process can be accelerated through the impellers, the filtering device can filter out residual impurities in gas, the adsorption devices at the two ends of the filtering device can wet the impurities in the gas, the impurities can be easily filtered out by the filtering device, and the service life of a draught fan is prolonged.