The invention discloses a down processing method with efficient impurity removal, which comprises the steps: washing raw down with clear water, dewatering, adding a humic acid compound, mixing well, cooling, filtering and spray-drying to obtain pretreated down; mixing the pretreated down, a degreasing agent, a detergent and water, washing, sterilizing via hot steam, and drying to obtain clean down. The humic acid compound is prepared by: mixing ferric chloride hexahydrate, ferrous sulfate heptahydrate and water, heating and stirring, adding a diethylamine solution, stirring uniformly, adding humic acid, a sorbitan fatty acid ester and corn protein powder, adjusting the temperature, stirring, adding hydroxyethyl cellulose, adjusting the temperature, and stirring to obtain the humic acid compound. According to the invention, impurities on the surface of fibers are efficiently bonded and sucked, the recycling rate is good, the surface smoothness of the down is increased, the dust contentof the down is reduced, the adhesion between the fibers can be reduced, the bulkiness of the down is improved, and meanwhile, the natural taste of the down can be removed and covered.