Abstract:A new triterpenoid saponin, anemoside A. was isolated from Anemone rivularis Buch.-Ham. ex DC. Its structure was elucidated as 3-O-[β-D-ribopyranosyl (1→3)-α-L- rhamnopyranosyl (1 -→ 2) -α-L-arabinopyranosyl]-oleanolic acid-E8-O-α-L-rhamnopyranosyl (1→ 4)-β-D-glucopyranoside by means of chemical methods and 1H-NMR. 13C-NMR, DEPT, MS spectral analyses.