From the methanol extract of the root of Polygonum hydropiper, a novel coumaryl glycoside hydropiperoside was isolated together with anthraquinone, ellagic acid 3,3'-di-O-methyl ether, gallic acid, two quercetin glycosides and an unidentified aromatic δ-lactone possessing antifertility activity. The structure of hydropiperoside was established as β-D-(1,3,6-tri-p-coumaryl)-fructofuranosyl-α-D-glucopyranoside by combination of extensive ¹H NMR and ¹³C NMR spectra, and the FD/MS spectrum.