A cationic graft-copolymer for a drug delivery system comprising a unit derived from a having a hydroxyl groups, namely, a cationic polysaccharide of the following formula (1) (C6H7O2(OH)3-a (OX)a)xH2O (1) and a unit derived from a polymerizable olefin compound of the following formula (2) (a, x, X, R4, R5, R6, and R7 are defined in claim 1-8) a process for preparing the same and a transfection reagent made therefrom.
