Starch graft copolymers were prepared from AM/DMDAAC by radiation grafting method in water media, and the resulting copolymers were analyzed by weight measurement and titration method. It was found that grafting ratio and grafting efficiency increased and then decreased with increasing absorbed doses meanwhile cationic degree and grafting efficiency of DMDAAC decreased and then increased with increasing absorbed doses. All of grafting ratio, grafting efficiency of total monomers, cationic degree and efficiency of DMDAAC were high at high reactant contents and low at low reactant contents in the polymerization recipe at absorbed dose of 3 kGy by use of 6:7:7 (w/w/w) ratio with starch?AM?DMDAAC.Cited