To investigate the levels and clinical significance of serum microRNA (miR)-146a, miR-145, T-helpertype17 (Th17)/regulatory T cell (Treg) in children with respiratory syncytial virus (RSV) infectious pneumonia. The clinical data of 200 children with RSV infectious pneumonia admitted to Nantong Maternal and Child Health Hospital from June 2020 to June 2023 were retrospectively collected as the study group. At the same time, 200 children with mycoplasma pneumonia were selected as the common pneumonia group and 200 healthy children were selected as the healthy group. The levels of serum inflammatory factors [interleukin-6 (IL-6), interferon-γ (IFN-γ), tumor necrosis factor-α (TNF-α)] were detected by enzyme-linked immunosorbent assay. The expression levels of serum miR-146a and miR-145 were detected by RT-qPCR. The levels of Th17/Treg were detected by flow cytometry. The levels of miR-146a, miR-145, Th17/Treg and serum inflammatory factors were compared among the three groups. Pearson method was used to analyze the correlation between miR-146a, miR-145, Th17/Treg and serum inflammatory factors in children with RSV infectious pneumonia. The receiver operating characteristic (ROC) curve was drawn to analyze the diagnostic value of miR-146a, miR-145, Th17/Treg in children with respiratory syncytial virus infection pneumonia. The results showed that in the study group, miR-146a (2.01±0.58), miR-145 (1.81±0.46), Th17/Treg (1.09±0.31), IL-6 (7.82±2.11) ng/L and TNF-α (9.82±2.96) ng/L were higher than those in the common pneumonia group miR-146a (1.49±0.42), miR-145 (1.43±0.31), Th17/Treg (0.77±0.24), IL-6 (5.89±1.32) ng/L, TNF-α (7.34±2.32) ng/L and healthy group miR-146a (1.25±0.19), miR-145 (1.19±0.16), Th17/Treg (0.38±0.09), IL-6 (4.52±1.04) ng/L, TNF-α (5.39±1.07)ng/L. The levels of the above indexes in the common pneumonia group were higher than those in the healthy group, and the differences were statistically significant (F=183.543, 175.938, 617.182, 226.657, 193.459, P<0.05). In the study group, IFN-γ (14.18±3.25) pg/ml was lower than that in the control group (19.52±5.13) pg/ml, but higher than that in the healthy group (9.77±2.40) pg/ml, and the difference was statistically significant (F=335.432, P<0.05). Pearson correlation analysis showed that miR-146a, miR-145 and Th17/Treg were positively correlated with IL-6 and TNF-α (P<0.05), but negatively correlated with IFN-γ (P<0.05). ROC curve results showed that the area under the curve (AUC) of miR-146a, miR-145 and Th17/Treg in the diagnosis of RSV infectious pneumonia was 0.767, 0.762 and 0.790, respectively, while the combined detection of the three was 0.904. In conclusion, the levels of miR-146a, miR-145 and Th17/Treg are highly expressed in children with RSV infectious pneumonia, and are closely related to the inflammatory response of children. The combined detection of the three may have certain application value in the auxiliary diagnosis of RSV infectious pneumonia.