The invention discloses a preparation method of food-grade aluminum-free disodium dihydrogen pyrophosphate with low gas emission volume. The preparation method comprises the following steps: filteringphosphoric acid and sodium hydroxide and regulating a temperature and concentration; adding phosphoric acid into a neutralization kettle, adding additives including calcium carbonate and potassium dihydrogen phosphate to obtain a mixture, and completely dissolving the mixture and then adding sodium hydroxide; controlling a reaction temperature and reaction end points after the sodium hydroxide solution is completely added, and curing to obtain a neutralized material; dropping the neutralized material into a powder spraying tower and performing powder spraying and drying to obtain anhydrous sodium dihydrogen phosphate powdery material; dropping the anhydrous sodium dihydrogen phosphate powdery material into a polyfurnace and performing polymerization, drying and sieving to prepare the aluminum-free disodium dihydrogen pyrophosphate with the low gas emission volume. According to the method disclosed by the invention, the additives including calcium carbonate and potassium dihydrogen phosphate are added, and the steps of the preparation method and parameters of the preparation method are optimized simultaneously, so that the problems that the size of a flour product made from disodium dihydrogen pyrophosphate is overlarge, a tissue structure is not exquisite and a taste is rough are solved, so that the products such as cakes and noodles are subjected to gas emission smoothly in aproduction process, the sizes of the products are uniform, the tissues are exquisite and the taste is superior.