Abstract: Corn starch was mechanically activated by ball milling( rolling- type) and then cross- linked by epichlorohydrin in aqueous slurry systems. The process of cross- link was studied with respect to the time of mechanical activation,reaction temperature,reaction time,dosage of cross- linking agent and p H.And the optimum reaction condition was determined by the quadratic regression orthogonal rotation design and response surface methodology.The results indicated that the mechanical activation considerably enhanced the cross- linking reaction of the corn starch,and the optimum reaction condition was reaction temperature 36.2℃,p H 9.7,reaction time100.7min.The sedimentation volume was 1.86 m L under this preparation condition.