OBJECT IVE To study the effects of ergosterol peroxide derivatives EP-3P on the proliferation ，migration and invasion of human tripe negative breast cancer cell MDA-MB- 231，and to provide reference for the development of breast cancer related drugs. METHODS MTT assay was adopted to detect the proliferation of MDA-MB- 231 cells after treated with 0（blank control），1.25，2.5，5，10，20，40 μmol/L EP-3P for 24，48 and 72 h. Wound healing assay and Transwell chamber method were adopted to detect the migration and invasion ability of MDA-MB- 231 cells after treated with 0（blank control ），5，10，20 EP-3P for 24 h. The apoptosis and cell cycle distribution were detected by flow cytometry. Western blot assay was used to detect the expressions of B-cell lympho ma-2（Bcl-2），Bcl-2 associated X protein （Bax），caspase-3，cleaved-caspase-3，cytochrome C （Cyt-C），matrix metalloproteinase- 2（MMP-2）and MMP- 9. RESULTS Compared with blank control group ，2.5，5，10，20，40 μmol/L EP-3P could significantly increase the inhibitory rate of cell proliferation （P＜0.05 or P＜0.01）in a dose and time- dependent manner. After 24 h treatment of EP- 3P（10，20 μmol/L），the rate of cell migration and the number of invasive cells were decreased significantly （P＜0.01），and cell was arrested at G 2/M stage （P＜0.05 or P＜0.01）；the apoptotic rate was increased significantly （P＜0.05）；the protein expressions of Bax ，Cyt-C and cleaved-caspase- 3 were upregulated significantly ， while those of Bcl- 2，caspase-3，MMP-2 and MMP- 9 were downregulated significantly （P＜0.01）. CONCLUSIONS EP-3P can inhibit the proliferation ，migration and invasion of human tripe negative breast cancer cells MDA-MB- 231 through mitochondrial mediated endogenous caspase pathway ，and induce the apoptosis of cells .