To investigate the effects of Ruanjian Xiaoliu Pill (RJXLp) drug serum on aromatase, estrogen receptor(ER) expression level, cell generation cycle and apoptosis in breast carcinoma cell line MCF-7 cells. Methods: RJXLp drug serum was prepared and MCF-7 cells were treated with it for 24, 48 and 96h respectively. Then the expression of aromatase and ER mRNA were analyzed by qRT-PCR, cell generation cycle and apoptosis were assayed by flow cytometry(FCM) and cell growth curve was determined by MTS. Results: After incubated in RJXLp drug serum for 24h, expression of CYP19 mRNA、ER mRNA of MCF-7 cells decreased significantly compared to control group (0.32 and 0.09 fold, respectively). For the cell generation cycle analysis, cell cycle process of MCF-7 cells was changed after 48h treatment with RJXLp drug serum. Cells in S and G2/M phase decreased, especially in G2/M phase, while cells in G0/G1 phase increased. Both early and late apoptosis cells increased compared with control group. MTS assay showed cell growth curve declined after incubated in drug serum for 48h for the drug serum group and inhibition effects reached the peak when incubated for 96h. Conclusion:RJXLp drug serum can inhibit estrogen biosynthesis, attenuate its effects, and suppress cell growth as well.