Preparation method of sodium dihydrogen phosphate monohydrate

The invention provides a sodium dihydrogen phosphate monohydrate preparation method, which comprises: 1) adding a sodium dihydrogen phosphate solid into a certain amount of purified water, and stirring, preferably, the amount of the purified water is 3-5 times of the mass volume of the sodium dihydrogen phosphate; 2) stirring at 0-40 DEG C for 2-24 hours, preferably at 20-30 DEG C, and stirring for 2 hours; (3) after stirring is finished, solid-liquid separation is carried out, sodium dihydrogen phosphate solids are obtained, and the solid-liquid separation can be selected from reduced-pressure suction filtration, centrifugation and filter pressing. And 4) drying under reduced pressure at 20-40 DEG C to obtain a sodium dihydrogen phosphate monohydrate product. The water content of the sodium dihydrogen phosphate prepared by the method meets the drying weight loss range (10.0%-15.0%) of the sodium dihydrogen phosphate quality standard of the second part of the Chinese pharmacopoeia 2020 edition, meanwhile, oth