Abstract: A method for preparing modified graft copolymers of cellulose with monovinyl monomers containing ionic groups or non-ionic groups capable of being converted to ionic ones involving a free-radical polymerization of said monovinyl monomers onto cellulose in the presence of a free-radical type initiator and modification of the resulting graft-copolymers of cellulose with said monovinyl monomers. The processes are performed in one stage in the presence of a modifying agent, that is, divinylbenzene taken in an amount ranging from 1 to 5 mol. % of the monovinyl monomer. The static exchange capacity of the modified graft copolymers of cellulose in the form of cationites is as high as 5 mg-equiv/g. The static exchange capacity of the graft copolymers of cellulose in the form of anionites is as high as 3.5 mg-equiv/g. The degree of swelling in water at a temperature of 20.degree. C. is within the range of from 180 to 200%. The modified graft copolymers of cellulose have a fibrous structure.