Abstract: Objective:To investigate the antioxidant effect of bioactive substances from tsao-ko in the aged ICR mice induced by D-galactose. Methods:Aged mice induced by high fat diet and D-galactose were feeding separately with different kinds of diets. High dose of tsao-ko was 200mg/kg, low dose of tsao-ko was 100mg/kg.The level of SOD, GSH, GSH-Px, MDA and 8-ISO-PGF2α in plasma, liver was investigated in aged mice in the experiment of the antioxidant activity in vivo. Results:Compared with the control group about the data of plasma, the activity of SOD in the aged mice conducted with tsao-ko was significantly improved (p<0.01) , the content of GSH of mice deposed with tsao-ko was significantly improved (p<0.01) , the activity of GSH-Px in the aged mice conducted with high dose of tsao-ko was significantly improved (p<0.01) , the content of MDA in the aged mice conducted with tsao-ko was lower (p<0.05) , the content of 8-ISO-PGF2α in the aged mice conduced with high doses of tsao-ko was lower (p<0.05) . Compared with the control group about the data of liver, the activity of SOD of mice conducted with low dose of tsao-ko was improved (p<0.05) and significantly improved with high dose (p<0.01) , the content of GSH in the aged mice conducted with high dose of tsao-ko was significantly improved (p<0.01) , the activity of GSH-Px of mice conducted with tsao-ko was improved significantly (p<0.01) , the content of MDA in the aged mice conducted with tsao-ko was lower significantly (p <0.01) . Conclusion:The methanol extract of tsao-ko could increase the level of SOD, GSH, GSH-Px and reduce MDA and 8-ISO-PGF2α.