Objective:To study the effects of pro-inflammatory cytokines on expression levels of microRNA-29 (miR-29) family and anti-apoptotic proteins in rat islet β cells. Methods: INS-1 cells, which belong to rat islet cells, were incubated in the presence or absence of a pro-inflammatory cytokine mixture (IL-1β10 ng/ml, TNF-α 50 ng/ml and IFN-γ50 ng/ml) for 24 h (the pro-inflammatory cytokine stimulated group and the control group). The function of INS-1 cells was evaluated by the glucose stimulating insulin releasing test. Cell apoptosis was detected by flow cytometry. The expression levels of miR-29 family and myeloid cell leukemia 1 (Mcl-1) mRNA, B-cell lymphoma (Bcl-2) mRNA in INS-1 cells were detected by real-time fluorescence quantitative PCR, and the protein expression levels of Mcl-1, Bcl-2 were detected by Western blot. Results:①The miR-29a and miR-29b expression levels were significantly increased in INS-1 cells stimulated by pro-inflammatory cytokine mixture,and the differences were statistically significant (P < 0.05). The expression level of miR-29c of the pro-inflammatory cytokine stimulated group was increased compared with the control group, but there was no statistical significance (P > 0.05). ②The mRNA expression levels of Mcl-1 and Bcl-2 in the pro-inflammatory cytokine stimulated group were decreased with no statistical significance (P > 0.05).③ In the pro-inflammatory cytokine stimulated group, the protein expression levels of Mcl-1 and Bcl-2 were downregulated, and the differences were statistically significant (P < 0.01). ④Pro-inflammatory cytokine mixture stimulated INS-1 cells led to a significant increase in cell death, and the difference was statistically significant (P < 0.05). Conclusion: Pro-inflammatory cytokines may downregulate the expressions of Mcl-1 and Bcl-2 through overexpressing miR-29 family, and then impact on apoptosis in pancreatic β cells, thereby trigger type 1 diabetes mellitus.