Objective:To observe the effect of Shugan Liangxue Decoction(舒肝凉血方,SGLXD) on estrogen receptor α (ER α) in human breast cancer cells.Methods:The effect of SGLXD (0.85-5.10 mg/mL) on the proliferation of breast cancer cells were evaluated by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay.The nuclear ER α protein levels in MCF-7,T47D and ZR-75-1 cells which treated by SGLXD for 24 h were examined by western blot and immunofluorescence assay.MCF-7 and MDA-MB-231 cells were treated by 17 β-estradiol (E2) with or without SGLXD,for 24 h,and the E2 targeted genes c-myc and bcl-2 protein product was evaluated by western blot.Results:SGLXD showed dose-dependent inhibition on the proliferation of MCF-7,T47D and ZR-75-1 cells,but did not inhibit the proliferation of MDA-MB-231 cells.Furthermore,the promotive effect on cell growth induced by E2 was also significantly inhibited by SGLXD treatment.With the treatment of 1.70,3.40,5.10 mg/mL SGLXD,the nuclear ER α protein level was reduced to 88.1％,70.4％ and 60.9％ in MCF-7 cells,and was decreased to 43.0％,38.4％ and 5.9％ in ZR-75-1 cells as compared with the control group.In T47D cells,the nuclear ER α protein was down-regulated to 51.3％ and 4.3％ by 3.40 and 5.10 mg/mL SGLXD treatment.The down-regulative effect of SGLXD on nuclear ERα was confirmed by immunofluorescence assay.SGLXD decreased the protein product of c-myc and bcl-2.Conclusions:SGLXD may exhibit selective inhibition effect on the proliferation of ER positive breast cancer cells.SGLXD reduced the nuclear ERα expression and the protein product of E2 target gene c-myc and bcl-2.