Chitosan pyruvic acid derivatives was successfully prepared from chitosan and pyruvic acid under reducing conditions, via aldimine formation. The chemical structure of the derivatives was proved by 13C NMR and IR. It was found ratio between glucose residues and pyruvic acid, reaction time, pH, and molecular weight of original chitosan had great influence on the degree of substitution (DS). N-(1-carboxyethyl) chitosan (N-CE-CTS) showed similar moisture absorption-retention curve and ability with HA, and much better ability than the original chitosan. Hydroxyl radical scavenging ratio of 4g/L chitosan and N-CE-CTS was 35.0% and 41.7%, respectively.