Cudrania tricuspidata Bereau (Moraceae) have been used for anti-inflammatory, anti-hepatotoxic, anti-hyper­tensive and anti-diabetic activities. In order to investigate the efficacy of antioxidant activity, the bio-activity guided fraction and isolation of Biologically active substance were performed. $H_{2}O,;30\%,;60\%,;100%$ MeOH and acetone fractions were examined on the antioxidant activity by DPPH method. It was shown that $30\%,;60\%,;100\%$ MeOH fractions have sig­nificantly antioxidant activity. From $30\%$ MeOH fraction, two dihydroflavonoid glycosides dihydroquercetin 7-O-$eta$-D-glu­copyranoside (I), dihydrokaempferol 7-O-$eta$-D-glucopyranoside (V) were isolated and $60\%$ MeOH fraction, six flavonoids including quercetin 3-O-$alpha$-L-rhamnopyranosyl($1 ightarrow6$)-$eta$-D-glucopyranoside (II), quercetin 3-O-$eta$-D-glucopyranoside (III), quercetin 7-O-$eta$-D-glucopyranoside (IV), kaempferol 3-O-$alpha$-L-rhamnopyranosyl($1 ightarrow6$)-$eta$-D-glucopyranoside (VI), kaempferol 3-O-$eta$-D-glucopyranoside (VII), kaempferol 7-O-$eta$-D-glucopyranoside (VIII) were isolated. To investigate the antioxidant activities of each compounds, we measured radical scavening activity with DPPH method and anti-lipid per­oxidative efficacy on low density lipoprotein (LDL) with TBARS assay. Four compounds of quercetin glycosides (I, II, III, IV) showed significant antioxidant activity.