The root of Aralia continentalis Kitagawa (Araliaceae) have been used as an analgesic and fever remedy, and for treatment of rheumatism in Chinese medicine, whereas the young leaves are used for ingredient of salad. Antioxidant activity of the young leaves of A. continentails was determined by measuring lipid peroxide produced when a mouse liver homogenate was exposed to the air at $37^{circ}C$, using 2-thiobarbituric acid (TBA) and by evaluation the radical scavenging activity on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. Chromatographic separation of active fraction led to the isolation of six flavonoids, among which quercetin, hyperoside and kaempferol showed strong antioxidant activities, while 6"-O-acetyl astragalin, astragalin and trifolin were inactive. Adenosine, oleanolic acid 28-O-glucosyl ester and salsoloside C methyl ester isolated from the somewhat active BuOH fraction exhibited no antioxidant activities.