The effect of antioxidant activity of soyasaponin on the liposomal phospholipid membrane were investigated by spectrophotometry. The oxidation index and oxidation rate of ${alpha}-tocopherol$ containing egg phosphatidylcholine (EPC) liposomes were markedly decreased in the presence of soyasaponin relative to those of purephospholipid liposmes. ${alpha}-tocopherol$ containing liposomes delayed the oxidation of liposomes. Especially soyasaponin stimulated the antioxidant activity of ${alpha}-tocopheroal$ in liposomes. These results indicates that soyasaponin in liposomes had some additive effect on antioxidant of ${alpha}-tocopherol$ toward liposomes.