PURPOSE: To prepare the titled cellulose efficiently and economically, useful as a cellulose model substance and additive for drugs or foods, etc., by physical treatment of cellulose followed by reaction with an inorganic acid.

CONSTITUTION: Cellulose is subjected to one of physical treatments selected from ball mill, colloid mill, extruder, exposive crushing and vibration type grinding treatments, followed by treatment with an inorganic acid (e.g. HF, HCl H2SO4, phosphoric acid, perchloric acid), thus obtaining the objective cellulose with a polymerization degree ≤100 (pref. 10W100). The water contents in the physical treatments described above, are pref, minimal (i.e, in a dry state) for ball mill and vibration type treatments, several tens-several hundress wt% for extruder and exposive crushing treatments, and such as to be in a 5W15% (on a cellulose weight basis) suspension aqueous solution for colloid mill treatment, respectively.