The aim of this work was to study the expression of SOX2 gene in triple negative breast cancer and its role. One hundred and twenty specimens of paraffin-embedded triple negative breast cancer (TNBC) tissues were collected from Harbin Medical University Cancer Hospital, Heilongjiang, China between January 2014 and March 2018. The expression of SOX2 was detected using immunohistochemistry, and the relationship between the expression of SOX2 and clinical features was analyzed. Breast cancer cell lines (normal group, SOX2 interference group, SOX2 overexpression group) were cultured in vitro to detect the proliferation and cloning ability of the cell lines. The expression of SOX2 was related to lymph node metastasis and stage of breast cancer (P less than 0.05), but was not related to age, menopause or tumor size (P > 0.05); the expression of SOX2 in the overexpression group was significantly greater than that in the normal group after 72 hours, and no significant difference between the overexpression group and the interference group was observed. The number of clone cells with a diameter of 0.5 mm in the interference group was lower compared to the normal group, and that of the overexpression group was higher, but not significant. SOX2 is associated with the high invasiveness of breast cancer and can be used as a therapeutic target to inhibit the metastasis of cancer cells. SOX2 can promote the proliferation of breast cancer cells and affect the size of clone cells in its involvement in clone.