The invention relates to a preparation method of envelopes of phosphoric acid micropore acidulant granules. The preparation method comprises the following specific steps: (1) mixing 10-15 parts of chitosan, 10-15 parts of citric acid, and 10-15 parts of malic acid to obtain a mixture A, screening the mixture with a sieve of 300 meshes, adding lactic acid and polyethylene glycol, uniformly mixing the screened mixture A, the lactic acid and the polyethylene glycol to obtain a mixture B, spraying the mixture B, and pelleting the sprayed mixture B; (2) uniformly mixing 3-5 parts of phosphoric acid, 1-2 parts of formic acid, 8-10 parts of acetic acid, 3-5 parts of propanoic acid, 8-10 parts of butyric acid, hydroxypropyl methyl cellulose, gas phase silicon dioxide and the pelleted mixture B obtained in the step (1) to obtain a mixture C, pelleting the mixture C by using a screw extruder, and oppositely impacting the pelleted mixture C by using airflows during pelleting; (3) and uniformly mixing 1-3 parts of phosphoric acid, 1-3 parts of fumaric acid, 5-10 parts of ethanol, 1-3 parts of benzoic acid, and 20-25 parts of melted polyacrylic resins to obtain a liquid lagging cover for lagging covers. According to the preparation method disclosed by the invention, the preparation technology is simple, the performance is stable, the storage is easy, the quality guarantee period is long, the preparation method has the notable effect of protecting the health of the alimentary canals of livestock, and the bioactivity of the livestock can be obviously improved.