A new tetrasaccharide flavonol glycoside was isolated from the aerial parts of Epimedium acuminatum, along with three known flavonoids. The structure of the new compound, named acuminatoside [1], was established to be anhydroicaritin-3-O-alpha-L-rhamnopyranosyl(1----2)-alpha-L-rhamno pyranoside-7- O-beta-D-glucopyranosyl-(1----2)-beta-D-glucopyranoside by means of spectroscopic techniques (uv, eims, fdms, fabms, 1H nmr, 1H-1H COSY, 2D-J, 13C nmr, APT, and 1H-13C HETCOR) and chemical methods (acid hydrolysis, enzymatic hydrolysis, and tlc-densitometry). The known compounds were identified as icariin, epimedoside A, and kaempferitrin.