OBJECTIVE： To study the effects of processed Polygonum multiflorum containing serum on the proliferation and the expression of estrogen receptor （ER） of human breast cancer T-47D cells， and to investigate its phytoestrogen （PE）-like effect. METHODS： Sexually immature SD rats were randomly divided into estradiol valerate （Ev） group （positive control， 0.12 mg/kg）， processed P. multiflorum low-dose and high-dose groups （0.75， 3 g/kg， by crude drug）， low-dose and high-dose processed P. multiflorum+Ev groups （same dose as single drug group）， with 10 rats in each group. Blank group was given constant volume of water intragastrically， and administration groups were given relevant medicine intragastrically； once day and night， for consecutive 4 days. Two hours after last administration， blank serum and containing serum were prepared. T-47D cells were also randomly divided into blank group， Ev group， low-dose and high-dose processed P. multiflorum groups， low-dose and high-dose processed P. multiflorum+Ev groups， and then were cultured in medium which contained 20％ blank serum or drug containing serum. CCK-8 assay was used to detect proliferation rate （PR）. Western blotting assay and RT-PCR were used to detect the protein and mRNA expression of ER-α and ER-β. RESULTS： Compared with blank group， PR of administration groups [each administration group （24 h）， other administration groups （48， 72 h） except for high-dose processed P. multiflorum+Ev group] were increased significantly； high-dose processed P. multiflorum group （72 h） was significantly higher than Ev group， and low-dose processed P. multiflorum+Ev group （72 h） was significantly higher than the same-dose processed P. multiflorum group； high-dose processed P. multiflorum+Ev group （72 h） was significantly lower than the same-dose processed P. multiflorum group （P＜0.05 or P＜0.01）. Relative protein expression of ER-α in Ev group， high-dose processed P. multiflorum group and low-dose processed P. multiflorum+Ev group， relative mRNA expression of ER-α and protein expression of ER-β in administration groups， relative mRNA expression of ER-β in Ev group， low-dose processed P. multiflorum group and processed P. multiflorum+Ev groups were all increased significantly. Relative protein and mRNA expression of ER-α in Ev group were significantly higher than processed P. multiflorum groups and combination groups. Relative protein and mRNA expression of ER-β in Ev group were significantly lower than low-dose processed P. multiflorum+Ev group， but relative mRNA expression of ER-β was significantly higher than processed P. multiflorum groups and high-dose processed P. multiflorum+Ev group. Relative protein and mRNA expression of ER-α and ER-β in low-dose processed P. multiflorum+Ev group as well as relative mRNA expression of ER-β in high-dose processed P. multiflorum+Ev group were significantly higher than the same-dose processed P. multiflorum group. Relative protein and mRNA expression of ER-α in high-dose processed P. multiflorum+Ev group were significantly lower than the same-dose processed P. multiflorum group （P＜0.05 or P＜0.01）. CONCLUSIONS： The processed P. multiflorum containing serum can promote the proliferation of human breast cancer T-47D cells， and play the PE-like role through promoting protein and mRNA expression of ER-α and ER-β. However， the above effects are weaker than estrogen， and the combination of the two may antagonize the effect of estrogen.