The purpose of this research is to study of inhibitory activity of protostane type triterpens against farnesyl-protein transferase (FPTase). The ingredients of Alismatis Rhizoma, alisol B 23-acetate, C 23-acetate, alisols B and A 24-acetate, and thirteen synthetic analogues from alisol B 23-acetate exhibited inhibition activity against FPTase by scintillation proximity assay method. As a result, alisol C 23-acetate, one of the constituents of Alismatis Rhizoma, the synthetic analogues carboxylated and hydroxylated on branch chain of protostane exhibited a significant inhibitory activity. However, the compounds significantly lowered the inhibitory activity, when there is no 3 position keto on protostane skeletone.