Firstly,carboxymethyl starches ( CMS) with high degree of substitution ( DS) were prepared from native corn starch via a reaction in aqueous alcohol.Secondly,the physicochemical properties of the prepared starches were measured and analyzed by means of FT-IR,SEM,XRD,DV-I Prime rotary viscometry and ultraviolet spectrophotometry,which were then compared with those of native corn starch.The results indicate that ( 1) after the reaction,native corn starch is successfully carboxymethylated with a DS of more than 1. 0,and starch granules are rough,swollen and cracked,with huge burst holes in the their center; ( 2) the crystalline sharp peaks of CMS damage and even disappear after the carboxymethylation; and ( 3) in comparison with native corn starch,CMS possesses much better transparency and freeze-thaw stability that are both positively related to DS.