Abstract: OBJECTIVE To investigate the correlation between the expression of miR-223 in peripheral blood and the regulatory immune function and clinical prognosis in children with sepsis. METHODS All 55 children with sepsis in the Department of Critical Care Medicine of Qinghai Women and Children’s Hospital from Aug. 2017 to Aug. 2019 were in the sepsis group. Thirty children with systemic inflammatory response syndrome and 40 healthy children who were admitted to the hospital in the same period were enrolled in the SIRS group and the control group, respectively. Real-time fluorescent quantitative reverse transcription PCR（RT-PCR） was used to detect the mRNA expression of miR-223 in human peripheral blood; enzyme-linked immunoassay was used to detect the level of interferon-γ（IFN-γ） in the patient's serum; indexes among the three groups were compared. The levels of miR-223, C-reactive protein（CRP）, procalcitonin（PCT）, blood lactate and IFN-γ were compared among the three groups and between children who survived and died after 7 days of hospitalization. Perason correlation analysis was used to analyze the correlation between miR-223 and CRP, PCT, blood lactate and IFN-γ levels. RESULTS The levels of miR-223, CRP, PCT, blood lactate and IFN-γ in the sepsis group was significantly higher than that in the SIRS group and the control group（P＜0.001）. After 7 days of ICU hospitalization, there were 10 deaths in the sepsis group, and the total fatality rate was 18.18%. The levels of miR-223, CRP, PCT, blood lactate and IFN-γ in the survival group were significantly lower than that in the death group when they were admitted to the hospital（P＜0.05）. The correlation analysis showed that the expression level of miR-223 in the peripheral blood of patients with sepsis was positively correlated with APACHE Ⅱ, SOFA score, serum CRP, PCT, blood lactate and IFN-γ levels（P＜0.05）. CONCLUSION Upregulated expression of miR-223 in peripheral blood of children with sepsis is related to body-regulated immune cytokines and clinical prognosis, and its immunological mechanism and clinical application value need to be further tested.