Abstract: A tertiary amine type cationic starch – starch–methylene dimethylamine hydrochloride (SMMAHC) with different degree of substitution (DS) was prepared by the reaction of corn starch with cationic reagent hydroxymethyl dimethylamine hydrochloride (HMMAHC) using dry process. The moisture-adsorption and retention ability was investigated. The results showed that the moisture-adsorption and retention ability of cationic starch increased with DS of cationic groups. Under the condition of relative humidity (RH) 81%, when the DS of cationic starches were 0.36 and 0.70, their moisture-adsorption abilities were equal to them of hyaluronic acid (HA) and glycerin respectively. At RH 43% and 15%, the moisture-retention ability of SMMAHC with DS of 0.70 was equal to hyaluronic acid, surpurior than glycerin. Moisture absorption kinetics of SMMAHC was preliminary studied, the pseudo-second order model of adsorption kinetic equation can characterize the adsorption process verywell and the relation coefficients are all higher than 0.999.