A new triterpenoid saponin,bacopasideⅨ,was isolated from the whole plant of Bacopa monniera(L.)Wettst.and its structure was elucidated as 3-O-{β-d-glucopyranosyl(1→4)[α-1-arabinofuranosyl-(1→2)]-β-d-glucop-yranosyl}-20-O-α-1-arabinopyranosyljujubogenin by spectroscopic methods and some chemical transformations. A new triterpenoid saponin, bacopaside IX, was isolated from the whole plant of Bacopa monniera (L.) Wettst. And its structure was elucidated as 3-O- {beta-d-glucopyranosyl (1 → 4) (1 → 2)] - β-d-glucop-yranosyl} -20-O-α-1-arabinopyranosyljujubogenin by spectroscopic methods and some chemical transformations.