Temperature demonstrated a greater influence on the crystallinity. For instance, increasing the temperature from 45 ◦ C to 55 ◦ C, the crystallinity increased by 5.83%. Furthermore, the crystallinity was related to the acid-to-pulp ratio. When increased the ratio from 8.5 mg/l to 9.5 mg/l, the crystallinity increased by 4.69%. The change of crystallinity became insignificant when the ratio was further increased to 10.5 mg/l. It could be observed that there was a tendency for the cellulose crystallinity to increase as the particle size became smaller.