Abstract: The aim of this research is to investigate the inhibitory effects of calpain inhibitors (ALLN and calpain inhibitor IV) on mammary epithelial-mesenchymal transition (EMT) of MCF-10A cells induced by fibronectin (FN). After FN treatment of MCF-10A cells for 48 h, cell migration and invasion were determined by scratch repair assay and matrigel coated transwell assay, respectively. Vimentin, E-cadherin, snail and calpain-2 protein expression were measured by Western blot. The results suggest that FN induced morphological changes in MCF-10A cells, significantly increased the migration and invasion abilities of MCF-10A cells, upregulated the expression of calpain-2, vimentin and snail, and downregulated the expression of E-cadherin. All such changes by FN were reversed with ALLN and calpain inhibitor IV. In conclusion, the upregulation of calpain-2 was involved in FN-induced EMT of MCF-10A mammary epithelial cells, which may be inhibited by ALLN and calpain inhibitor IV.