【Abstract】Objective To observe the effect of Telocinobufagin on migration, invasion and epithelialmesenchymal transition (EMT) and mechanism research of breast cancer cell line 4T1. Methods 4T1 cells with different concentrations of Telocinobufagin (0, 005, 01, 05, 1, 125 and 15 μg/mL) were cultured for 24 h. MTT test was used to access to proliferation of 4T1 cells. The experiment was divided into the control group (0 mu g/ml) and the experimental group (005, 05 mu g/ml). The migration and invasion ability was tested by wound healing assay and transwell assay. The expression levels of Ecadherin, Vimentin and Fibronectin by immunofluorescence and western blot. The expression levels of Snail, pAkt and pmTOR by western blot. Results The MTT test showed that low concentration of Telocinobufagin (0, 005, 01, 05 and 1μg/mL) had no inhibitory effect on the proliferation of 4T1 cells, high concentration of Telocinobufagin (125 and 15μg/mL) had inhibitory effect on the proliferation of 4T1 cells. wound healing assay revealed that cell migration rations were respectively (858±52)%, (493±45)% and (303±45)% (F=105686, P＜005). Transwell migration assay found that the cell number was respectively1817±167, 88± 116 and 327± 52 (F=157909, P＜005). Transwell invasion assay found that the cell number was respectively 1422±149, 552±93 and 275±71(F=118766, P＜005). Immunofluorescence showed that Ecadherin was upregulated, Vimentin and Fibronectin were downregulated. Western blotting showed that the expression of Ecadherin was increased, P＜005; the expression of Vimentin, Fibronectin, transcription factor Snail, pAkt, pmTOR were decreased, P＜005. Conclusion Telocinobufagin inhibited epithelial mesenchymal transition of breast cancer 4T1 cells via Akt/mTOR/Snail pathway.