Objective To analyze the value of peripheral blood T-lymphocyte subsets and cytokines in the diagnosis of Mycoplasma pneumoniae pneumonia(MPP)in children.Methods A total of 120 children with MPP who were admitted to the hospital from January 2020 to January 2023 were selected as the observation group,80 children with pulmonary tuberculosis(TB)were selected as the control group.During the same pe-riod,120 healthy children who were examined at the hospital check-up center were selected as the health group.The clinical data from each group were retrospective analyzed,and fasting venous blood from subjects was collected.The levels of T-lymphocyte subsets CD3+,CD4+and CD8+were detected by flow cytometry in each group,and the CD4+/CD8+was calculated.The levels of interferon(IFN)-y,interleukin-8(IL-8),inter-leukin-10(IL-10)and interleukin-13(IL-13)were measured by enzyme-linked immunosorbent assay,and the levels of peripheral blood T-lymphocyte subsets and cytokines in each group were compared.The receiver op-erating characteristic(ROC)curve was used to assess the value of peripheral blood T-lymphocyte subsets and cytokines in the diagnosis of MPP in children.Results The levels of CD3+,CD4+,CD4+/CD8+,IL-13,and IL-10 in the observation group and control group were significantly lower than those in the health group(P＜0.05),while CD8+,IL-8,and IFN-γ levels were significantly higher than those in the health group(P＜0.05).Compared with the control group,the observation group had higher levels of CD3+,CD8+,IL-8,IFN-γand lower levels of CD4+,CD4+/CD8+(P＜0.05),and there were no statistically significant differences in IL-8 and IL-13 levels between the two groups(P＞0.05).The ROC curve results showed that the area under the curve(AUC)or CD3+,CD4+,CD8+,CD4+/CD8+,IL-8,IFN-γ,IL-13,and IL-10 for the diagnosis of MPP in children were 0.751,0.687,0.784,0.864,0.798,0.672,0.650,and 0.811,and AUC of the combined detection was 0.924.Conclusion Children with TB and MPP have significantly decreased immune function in the early stages of the disease,and abnormal expression of peripheral blood T-lymphocyte subsets and cytokines.Com-pared with TB children,MPP children have lower levels of CD4+,CD4+/CD8+,and higher levels of CD3+,CD8+,IL-10 and IFN-γ,and the T-lymphocyte subsets and cytokine levels are closely related to the changes in the patients'condition.The combined detection of CD3+,CD4+,CD8+,CD4+/CD8+,IL-8,IFN-γ,IL-13 and IL-10 provides a theoretical basis for identifying and diagnosing early MPP in children.