Abstract: Objective To investigate the differences between breast cancer cell line MCF-7／ADM resistant to adriamycin（ADM） and sensitive cell line MCF-7／S in proportion of breast cancer stem cells（BCSCs） and expression levels of breast cancer resistance protein（BCRP） and Pglycoprotein（P-gp），and to further observe the effects of traditional Chinese medicine β-elemene（β-ELE） on BCSCs and expressions of BCRP and P-gp. Methods MCF-7／ADM and MCF-7／S cell lines were cultured in the serumfree medium（SFM） and microspheres formation ratio was observed under phase contrast microscope. The expression levels of resistance genes BCRP and P-gp were detected by RTPCR. The ratio of BCRP and Pgp positive cells and percentage of CD44+CD24-／low subpopulation were analyzed by flow cytometry. The microsphere formation ratio and the expressions of BCRP, Pgp protein and mRNA in cell line MCF-7/ADM were detected after being treated by 15μg/ml β-ELE for 48h. Results The results of morphology and RTPCR indicated that microspheres formation ratio in the SFM and expression levels of BCRP and P-gp in MCF-7／ADM were higher than those in MCF-7／S.The flow cytometry analysis showed the positive rates of protein expressions of BCRP and P-gp in MCF-7／ADM were （77.78±9.55）％ and （32.33±5.12）％， and the percentage of CD44+CD24-／low subpopulation was （64.79±11.78）％， significantly higher than （3.97±1.51）％，（14.26±2.51）％，（18.79±3.28）％ in MCF-7／S with statistically significant differences. β-ELE inhibited obviously microspheres formation ratio， decreased mRNA and protein levels of BCRP and P-gp. Conclusion MCF-7／ADM cell line is a resistant cell population which enriched relatively BCSCs and highexpressed resistance proteins. β-ELE can inhibit proportion of BCSCs and microspheres formation ratio， and reduce the expression levels of resistance proteins in MCF-7／ADM.