Influence of the dextran-acrylamide copolymer structure on the sedimentation rate of a kaolin suspension has been examined. The flocculation efficiency has been evaluated, by measuring the turbidity of a suspension top layer by nephelometry. The size of kaolin clusters is estimated by means of microphotographs. It is found that dextran-backbone copolymers obtained by grafting long polyacrylamide chains possess the best flocculation abilities. Doses of dextran-graft-polyacrylamide copolymers sufficient for the effective sedimentation of low-concentrated kaolin suspensions are higher than those for high-concentration kaolin suspensions.