The invention discloses a preparation formula of a dihydric phosphate explosion suppressant. The method particularly comprises the following steps that 1, phosphoric acid and sodium carbonate are weighed and matched according to the proportion of 2.3:1; 2, a sodium dihydrogen phosphate solution is generated; 3, when the sodium dihydrogen phosphate solution generated in the step 2 is tested, the PHvalue of the solution is tested; 4, sodium dihydrogen phosphate with the adjusted ph value in the step 3 is placed on an evaporating dish to be heated, evaporated and concentrated, when cooling is conducted to reach 60-70 DEG C, crystals are sucked out, and sodium dihydrogen phosphate dihydrate is obtained; 5, sodium dihydrogen phosphate anhydrous is obtained. In the preparation formula of the dihydric phosphate explosion suppressant, the sodium carbonate solution temperature is 55-70 DEG C, the saline water temperature is not higher than the temperature of a synthetic groove, the phenomenonthat a sodium carbonate saturated solution is supersaturated in a synthetic reaction due to the fact that the temperature is lowered, so that a sodium hydrogen bisphosphate solid is separated out to affect the reaction effect is avoided, energy consumption of the by-product sodium carbonate solution in the concentration process is reduced, and the cost is lowered.