Abstract: AIM: To study the metabolism of ginsenosid Rb₁(G-Rb₁) by rat and human intestinal bacteria in vitro and in vivo. METHODS: Using thin-layer chromatography(TLC) and electron spurt ion mass (ESI-MS) for measurements of G-Rb₁ and its metabolites. RESULTS: G-Rb₁ was decomposed easily in vitro by rat and human intestinal bacteria, and consequently four metabolites (Rd, Rg₃/F₂, Rh₂/C-K and Ppd) were observed on TLC with prolongation of incubation time. Using electron spurt ion mass spectroscopy(ESI-MS), G-Rb₁ and its metabolites in rat feces were also assayed 4 h and 6 h after oral administration. Both metabolites Rd and Rg₃/F₂ were detected. CONCLUSION: The above mentioned results showed that the mode of metabolism of G-Rb₁ was Rb₁→Rd→F2→C-K and the final metabolite was 20(S) Ppd in the feces of rats and human.