FIELD : pulp industry.SUBSTANCE : invention relates to a method of activating cellulose by steam explosion in an alkaline medium. Method for activation of cellulose by steam explosion involves the following steps : mixing cellulose-containing material in an alkaline solution, blowing with nitrogen, heating to required temperature for 20–30 minutes, holding under excess pressure, complete depressurisation during 10 s, washing with water and drying. Pressure is released via drain valve with safety net. Cellulose ethers can be obtained from cellulose obtained using said method : methylhydroxypropyl cellulose, oxypropyl cellulose, ethyl cellulose, methyl cellulose, cyanoethyl cellulose. Cellulose ethers serve as thickeners, stabilizers and precursors and can be used in chemical, pharmaceutical, food, cosmetic, printing and other industries. During treatment of cellulose material, due to sharp opening of drain valve, pressure in device performing thermal exposure sharply decreases, due to which instantaneous effervescence of liquid phase throughout the volume, including inside plant fibers, with formation of steam. Hydrolysis liquid in form of steam is ejected via drain valve, and cellulose fibers remain in the device performing thermal exposure under pressure, due to available safety net. Formed inside the fiber pairs has volume approximately 1, 200 times greater than volume of water.EFFECT : due to sharp boiling, additional physical action takes place in the form of cellulose fiber breakage by steam bubbles, which results in loosening of their supramolecular structure, which further facilitates access of reagents and removal of reaction products both during preparatory operations, and during further production of cellulose esters.1 cl, 3 tbl