Abstract: The vinegar-egg was hydrolyzed by pepsin, and then hydrolysates were modified by plastein reaction with the same pepsin and amino acid.The influences of plastein reaction conditions on plastein yield and antioxidant activity of products were investigated.The result showed that the optimum plastein reaction conditions were as follows:amino acid was tryptophan, molar ratio of tryptophan to total free amino groups in vinegar-egg peptides was 1, concentration of vinegar-egg hydrolysates was 40%, temperature of plastein reaction was 65℃, pH was 6.0, and time was 6h.The antioxidant activity of modified vinegar-egg hydrolysates was improved by plastein reaction.The result of SDS-PAGE indicated that the composition of modified vinegar-egg hydrolysates was different from that of vinegar-egg hydrolysates and some new peptides with higher molecular weights were generated.