Abstract: Objective:To discuss the influence of ALDH 1+ and CD 133+ phenotypic breast cancer stem- like cells in TA2 triple negative breast cancer on promoting epithelial-mesenchymal transition (EMT) occurrence in TA2 mice with triple-negative breast cancer and on their biological behavior. Methods:Flow cytometry was performed to analyze the markers ALDH 1 and CD 133 in TA2 mice triple nega-tive breast cancer and breast cancer stem- like cells with ALDH 1+, ALDH 1−, CD 133+, and CD 133−phenotypes, which were sorted out.Then, the TA2 mice were inoculated with sorted tumor cells according to cell type. The mice were divided into ALDH1+, ALDH 1−,CD133+, and CD 133-groups. The tumor- growing conditions were observed. A tumor tissue was sliced for the immunohistochemical testing of ALDH 1−, CD 133−, and EMT-related Twist 1, E-cadherin, and VE-cadherin proteins. The expression difference of breast cancer stem cell surface markers ALDH 1 and CD 133 in triple-negative breast cancer and EMT-related proteins Twist 1, E-cadherin, and VE-cad -herin was analyzed.Results: The expression rates of breast cancer stem cell markers ALDH 1 and CD133 in TA2 mice triple negative breast cancer were 31. 2% and 6. 5% , respectively. The tumor growth ability of TA2 mice from ALDH1+group was obviously stronger than that from ALDH 1− group. The CD 133+ group was evidently stronger than CD133− group. The immunohistochemical results showed that ALDH1, Twist 1, and VE-cadherin expression levels in the ALDH 1+ group were evidently higher than that in the ALDH 1 − group (all P<0. 05). E-cadherin expression decreased ( P<0. 05). CD 133−, Twist 1, and VE-cadherin expression levels in CD 133+ group were higher than that in CD133− group (all P<0. 05). Conclusion: In TA2 mice triple negative breast cancer, ALDH1+ and CD 133 + phenotypic breast cancer stem-like cells may influence the expression of EMT-related proteins, and promote the formation of triple-negative breast cancer.