Abstract:Objective: To investigate the triterpenoids chemical constituents in rhizome of Alisma gramineum. Method: Silicon gel chromatography and HPLC techniques were employed for isolation and purification of the constituents, and the structures were elucidated by various spectral analyses such as NMR, MS and IR. Result: 5 protostane-type tetracyclic triterpenoids were isolated and identified as 16,23-oxidoalisol B(1) , 11-deoxyalisol C(2) , alisol F(3) , 16β-methoxyalisol B acetate (4) , 16β-hydroxyalisol B acetate (5) . Conclusion: All of these compounds were found from A. gramineum for the first time.