Objective To investigate the expressions of miR-125b and target gene Raf1 proto-oncogene serine/threonine protein kinase (RAF1) in peripheral blood mononuclear cells (PBMCs) of pediatric patients with pulmonary tuberculosis (PTB), and observe the regulation of miR-125b on macrophage apoptosis and activity. Methods PBMCs of patients with PTB and healthy children were collected and separated. Real-time fluorescence quantitative PCR was used to detect mRNA expression level of miR-125b and RAF1, and Western blotting was used to detect the protein level of RAF1. THP-1 macrophages were transfected into miR-125b mimic, negative control mimic (NC-mimic), miR-125b inhibitor and negative control inhibitor (NC-inhibitor), which were cultured for 48 hours. Western blotting was performed to observe the expression of RAF1 in THP-1 macrophages, annexin V-FITC/PI double staining combined with flow cytometry was used to test cell apoptosis, and CCK-8 assay was used to detect cell proliferation. Results The expression of miR-125b in PBMCs in pediatric patients with PTB was downregulated, and mRNA and protein levels of RAF1 were upregulated. When miR-125b was over-expressed in THP-1 macrophages, the expression of RAF1 was reduced to promote the apoptosis of macrophages and decrease cell activity; when the expression of miR-125b was inhibited in THP-1 macrophages, the expression of RAF1 was elevatedand the apoptosis of macrophages was inhibited, the cell activity was promoted. Conclusion In PBMCs of children with PTB, miR-125b level is low. Upregulation of miR-125b in THP-1 macrophages, the apoptosis of THP-1 macrophages is promoted and cell activity is inhibited.