In order to find the antioxidative components, fractionation of Cyperus amuricus (Cyperaceae) methanol extract was performed by measuring the DPPH (1,1-diphenyl-2-picrylhydrazyl) scavenging effect. Three compounds, 3,4-dimethoxy benzoic acid (1), 4-hydroxybenzoic acid (2), and piceatannol (3) were isolated from the active ethylacetate soluble fraction of C. amuricus through repeated silica gel and Sephadex LH-20 column chromatography. Among them, compound 3 showed the significant antioxidative effect on DPPH free radical scavenging test. These compounds are reported for the first time from this plant.