Yeast based estrogenicity assay is the simplest and useful for the assay and the discovery of novel estrogenic substances in natural specimens, The estrogen receptor(ER) modulation activity of 50% EtOH extracts of 101 traditional medicinal herbs was assessed using a recombinant yeast assay system with both a human estrogen receptor expression plasmid and a receptor plasmid. Among them, 14 species proved to be active. Pureariae Flos (flower of Puerraria thunbergiana BENTH.) had the highest estrogenic relative potency$(7.75{ imes}10^{-3})$ $(EC_{50}=9.39;{mu}g/ml)$. The $EC_{50}$ value of $17{eta}-estradiol$ used as the positive control was $0.073;{mu}g/ml)$ (Relative Potency=1.00). There results demonstrated that some of the traditional medical herb may be useful in the therapy of estrogen replacement.