Objective To investigate the effects of the rhein on the mitochondria fission and epithelial-mesenchymal transition(EMT)of breast cancer cells MDA-MB-231.Methods Human breast cancer cells were intervened with rhein,and the cells were divided into control group(0 μmol·L-1),low dose rhein group(100 μmol·L-1),and high dose rhein group(200 μmol·L-1).The proliferation activity of the cells was detected by CCK-8,and migrations was detected by Scratch-healing migration assay.The morphology and distribution of mitochondria were detected by transmission electron microscope,and the expression levels of Dynamin-related protein 1(Drp1),mitofusin2(Mfn2),E-cadherin,Vimentin proteins were detected by Western blot.Results Compared with control group,Rhein significantly reduced the protein expression of Drp1、Vimentin(P<0.05),and increased E-cadherin and Mfn2,thus down-regulating mitochondria fission,inhibiting cell proliferation and migration.High dose Rhein was better than low dose.Conclusion Rhein can inhibit the proliferation and migration of breast cancer cells by reducing the expression of Drp1,Vimentin and up-regulating Mfn2,E-cadherin proteins.