Abstract: Objective To investigate the prognosis of triple-negative breast cancer and its relevance to epithelial-mesenchymal transition(EMT). Methods Two hundred and forty patients of breast cancer were classified into 3 groups，triple-negative group，receptor positive group and Her-2 positive group，according to the expression of estrogen receptor and progesterone receptor as well as Her-2 protein.Paraffin-embedded specimens of the primary tumors were collected and tissue micro-array blocks were constructed.Vimentin expressions were detected by imunohistochemistry.The prognosis and vimentin expression among the 3 groups were analyzed. Results The overall survival and the 5 year survival rate of triple-negative group were significantly decreased compared to receptor positive group，but were not statistically different from those of Her-2 group. Conclusion The poor prognosis of triple-negative breast cancer was associated with EMT.