An organopolysiloxane-modified polysaccharide prepared by esterification reacting (A) an organopolysiloxane having residual carboxylic anhydride groups and (B) a polysaccharide having hydroxyl groups, wherein the organopolysiloxane is bonded to the polysaccharide through half ester groups, and a process for the preparation of organopolysiloxane-modified polysaccharide, in which component (A) and component (B) are subjected to an esterification reaction in the presence of (C) a non-protonic polar solvent. The organopolysiloxane-modified polysaccharide comprising polysaccharide and organopolysiloxane bonded thereto through half ester groups is novel. The process for the preparation of organopolysiloxane-modified polysaccharide permits introduction of organopolysiloxane into polysaccharide at a high introduction ratio.