Objective：To investigate the function of oncogene c-Src in the process of anti-estrogen receptor α therapy and how it mediates the resistance in estrogen receptor（ER）-positive breast cancer cells. Methods：Wild-type MCF-7 cells were long-term treated with tamoxifen（TAM） and established tamoxifen resistant cells（TAM-R）. The expression of c-Src，ERα，and epithelial growth factor receptor（EGFR） was detected by immunoblotting. The interactions between ERα and EGFR were measured by immunoprecipitation. The c-Src inhibitor PP2 was used to block the tyrosine kinase activity of c-Src. Results：Compared with wild-type MCF-7 cells，expression levels of ERα，EGFR，and c-Src were not altered in TAM-R cells. However，the phosphorylation of c-Src was increased in TAM-R cells. Further examination demonstrated that interaction between ERα and EGFR was increased in TAM-R cells. Blocking c-Src phosphorylation by PP2 dissociated the interaction between ERα and EGFR in TAM-R cells. Importantly， TAM could onceagain remarkably inhibit cell growth of TAM-R cells after treated by PP2. Thus，the c-Src inhibitor could reverse TAM-R cells to TAM-sensitive cells. Conclusion：Our results suggested that c-Src is a critical molecule to mediate tamoxifen resistance in breast cancer cells through increasing the interaction between ERα and EGFR. Blocking interaction between ERα and EGFR by PP2 can recover the sensitivity to TAM in resistant cells. All of these findings demonstrated that the c-Src inhibitor can be alternatively used with ERα target therapy to treat ER-positive breast cancer thereby improving the therapeutic effects on breast cancer patients.