Abstract: AimTo set out the procedure for estimation of measurement uncertainty for the determination of ginsenosides R_g1, R_e and R_b1 in Radix ginseng by HPLC. MethodsTo facilitate the identification and analysis of the uncertainty sources arising from the procedure of analysis, a cause and effect diagram was constructed and simplified. Each uncertainty component, whether associated with individual sources or with the combined effects of several sources, was evaluated with respect to the significance of its contribution to the overall measurement uncertainty and was expressed as standard uncertainty. All the standard uncertainties were then combined according to the appropriate rules to give a combined standard uncertainty and an expanded standard uncertainty. ResultsThe expanded standard uncertainties for the HPLC determination of ginsenoside R_g1, R_e and R_b1 are 0.12c，0.14c and 0.13c, respectively. ConclusionMeasurement uncertainty is applicable to set the limit of the ginsenosides in Radix ginseng. The establishment of the methodology for the evaluation of measurement uncertainty is important to the studies of Chinese materia medica standards.