The invention provides a method for preparing high-purity sodium hypophosphite, which comprises the following processing steps: matching materials, wherein, the high-purity sodium hypophosphite is prepared from the following components according to proportioning by weight: 100 portions of yellow phosphorus, 70 portions of lime, 290 portions of ionic-membrane caustic soda and 500 portions of water;evenly mixing the components and reacting to obtain sodium hypophosphite solution and calcium phosphate precipitation; adding barium hypophosphate prepared from hypophosphorous acid and barium carbonate to the sodium hypophosphite solution, and evenly mixing the solution; improving the purity of the product solution by a method of adding powdered activated carbon for decoloring and adsorbing chloride ions; filtering with a membrane filtering machine with the pore diameter being 0.2 mum, so as to trap the tiny impurities; and additionally arranging a spraying system on a centrifuge and washingcrystals with de-ionized water solvent. The invention has the advantages that the crystals are sprayed and washed at the time of centrifugal separation, and the mother solution adhered to the surfaces of the crystals can be washed away, thereby ensuring the obvious purification effect; the method can remove the cumbersome and low-efficiency preparation process, simplify the preparation process and reduce the preparation cost; and the content of the product can reach 103.56%.