The methanol extract obtained from the aerial parts of Aceriphyllum rossii (Saxifragaceae) was fractionated into ethyl acetate (EtOAc), n-BuOH and $H_2O$ layers through solvent fractionation. Repeated silica gel column chromatography of EtOAc and n-BuOH layers afforded six flavonol glycosides. They were identified as kaempferol 3-O-$eta$-D-glucopyranoside (astragalin, 1), quercetin 3-O-$eta$-D-glucopyranoside (isoquercitrin, 2), kaempferol 3-O-$alpha$-L-rhamnopyranosyl $(1{ o}6)-eta$-D-glucopyranoside (3), quercetin 3-O$alpha$-L-rharnnopyranosyl $(1{ o}6)-eta$-D-qlucopyrano-side (rutin, 4), kaempferol 3-O-[$alpha$-L-rharnnopyranosyl $(1{ o}4)-alpha$-L-rhamnopyranosyl $(1{ o}6)-eta$-D-glucopyranoside] (5) and quercetin 3-O-[$alpha$-L-rhamnopyranosyl $(1{ o}4)alpha$-L-rhamnopyranosyl $(1{ o}6)eta$-D-glucopyranoside] (6) on the basis of several spectral data. The antioxidant activity of the six compounds was investigated using two free radicals such as the ABTS free radical and superoxide anion radical. Compound 1 exhibited the highest antioxidant activity in the ABTS ${2,2-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid)}$ radical scavenging method. 100 mg/L of compound 1 was equivalent to $72.1pm1.4;mg/L$ of vitamin C, and those of compounds 3 and 5 were equivalent to $62.7pm0.5;mg/L$ and $54.3pm1.3;mg/L$ of vitamin C, respectively. And in the superoxide anion radical scavenging method, compound 5 exhibited the highest activity with an $IC_{50}$ value of $17.6{pm}0.3{mu}M$. In addition, some physical and spectral data of the flavonoids were confirmed.