Abstract: Objective To investigate the expression level and role of Krüpple-like factor 4 (KLF4) in tumor necrosis factor α (TNFα) stimulated breast cancer cells SK-BR-3, and to identify the related mechanism. Methods Breast cancer cells SK-BR-3 were stimulated by TNFα at different concentrations (0, 1, 5, 10, 20 ng/mL) for 24 h. Adenovirus expression vectors of pAd-GFP and pAd-GFP-KLF4 were constructed and used to infect breast cancer cells SK-BR-3.Western blot was performed to detect KLF4 expression level. Flow cytometry and DAPI staining were used to investigate cell apoptosis. Results KLF4 expression levels were increased significantly in TNFα-stimulated breast cancer cells SK-BR-3 with more TNFα concentration. Flow cytometry and DAPI staining results showed that TNFα induced SK-BR-3 apoptosis. Flow cytometry results showed KLF4 overexpression promoted the apoptosis of TNFα-stimulated breast cancer cells SK-BR-3. Conclusion TNFα could induce KLF4 expression in breast cancer cells SK-BR-3, and KLF4 participates in cell apoptosis of TNFα-induced breast cancer cells SK-BR-3.