Objective:To establish a quantitative analysis of multi-components by single-marker (QAMS) HPLC method for the determination of five triterpenoid saponins in the intermediates of Bacopa monnieri. Methods BacopasideⅠwas used as the internal marker to establish relative correction factor (RCF) between BacopasideⅠand other four triterpenoid saponins, and RCF was used in the calculation of their content. Relative error was used in the appraisal of the result between external standard method and QAMS.  Results: The RCF between BacopasideⅠand other four triterpenoid saponins were 0.980,0.747,1.046 and 0.836, respectively. The two methods did not show significant difference in assay results and the RCFs were reliable with the relative error less than 5%.  Conclusion: The established QAMS method is feasible, accurate, simple and can be used as a method for the determination of multi-component index in the extract of Bacopa monnieri.