Abstract:To explore the value of T cell subsets and procalcitonin (PCT) monitoring in the diagnosis and treatment of Mycoplasma pneumonia (MPP) in preschool children. Methods Ninety-one children with MPP in our hospital were selected as the research objects (experimental group) and divided into combined bacterial infection group and simple MPP group according to whether the patients had bacterial infection, 61 children with normal physical examination in the same period were selected as the healthy control group. T lymphocyte subsets and PCT levels were dynamically monitored during clinical treatment, the differences were compared among the groups. Results The proportion of CD4+ T cells and PCT level in the MPP group were significantly higher than those in the combined infection group (p <0.05). After treatment, there was no significant difference in CD4+ T cells, CD8+ T cells or CD4+ T cells / CD8+ T cells ratio between the two experimental groups and the control group (p > 0.05). However, the PCT level of the combined infection group was still significantly higher than that of the control group and the MPP group (p < 0.05). Conclusions CD4+T cells and PCT level monitoring has certain guiding significance in the diagnosis and treatment of patients with MPP and merger of bacterial infection.