Preparation method of microcrystalline cellulose

The invention discloses a preparation method of microcrystalline cellulose. The preparation method comprises steps of pretreatment, degradation, washing, drying, and smashing and sieving. According to the preparation method, microcrystalline cellulose is prepared from, by weight, 65 to 75 parts of cotton powder, 0.4 to 1 part of hydrochloric acid, and 24 to 34 parts of water. Advantages of the preparation method are that: (1) refined cotton is subjected to pre-smashing and sieving so as to increase uniformity of solid phase reaction; (2) the preparation method is different from conventional hydrochloric acid aqueous solution hydrolysis, dry process is adopted, solid phase reaction is adopted, solid-phase cotton powder is subjected to rapid degradation in hydrochloric acid steam, polymerization degree is reduced, and using amount of hydrochloric acid is reduced greatly; and (3) water consumed by hydrolysis reaction is reduced, hydrochloric acid dosage is less, material washing is convenient to carry out, washing water is reduced relatively, environmental pollution is reduced, and cost is reduced.