Abstract： Objective:To study the effects of hyperbaric oxygen combined with high-dose Vitamin C（Vit C）on serum miR-146b，ischemia modified albumin（IMA），and immune function in children with viral myocarditis.Methods:A total of 260 children with viral myocarditis admitted and treated in Shanxi Children’s Hospital from February 2020 to January 2022 were selected and randomly divided into control group and study group，with 130 cases in each group. Both groups received the same comprehensive treatment such as bed rest，heart failure correction，oxygen inhalation，and cardiac drugs. In the control group，a high-dose Vit C was injected intravenously；while the study group was treated with HBO in addition to the treatment of the control group. Comparison of efficacy was made after two courses of treatment. Fasting venous blood was collected before and after treatment. Serum creatine kinase（CK）level was measured by phosphocreatine substrate assay，serum creatine kinase isoenzyme（CK-MB）level was tested by immunosuppressive assay，serum cardiac troponin I（cTnI）level was tested by Roche biochemical assay，serum lactate dehydrogenase（LDH）level was tested by colorimetric assay，and serum malondialdehyde（MDA）level was tested by thiobarbituric acid assay. The level of reduced glutathione（GSH）was measured by microplate assay，superoxide dismutase（SOD）level was tested by hydroxylamine assay，inducible nitric oxide synthase（iNOS）level was tested by colorimetric assay，CD3 +，CD4 +，and CD4 +/CD8 + ratios levels were tested by flow cytometry，mir-146b level was tested by RT-PCR experiments，and IMA level was tested by albumin cobalt binding assay. Results:The total effective rates of clinical treatment in the study group and the control group were 92.31% and 70.77%，respectively，and the difference between the two groups was statistically significant（ χ２=11.031 ，P=0.007）. Compared with those before treatment，the children in both groups after treatment had significantly lower levels of CK-MB，CK，cTnI，and LDH；after treatment，those indexes in the study group were significantly lower than those in the control group（ P<0.05）. Compared with those before treatment，the children in both groups after treatment had significantly lower levels of MDA and iNOS and significantly higher levels of GSH and SOD；and in the study group after treatment，the levels of MDA and iNOS were significantly lower than those in the control group，and the levels of GSH and SOD were significantly higher than those in the control group，all with statistically significant differences（ P<0.05）. Compared with those before treatment，the levels of CD3 +，CD4 +，and CD4 +/CD8 + in both groups after treatment were all significantly increased；after treatment，those indexes in the study were significantly higher than those in the control group（ P<0.05）. Compared with those before treatment，the expression levels of miR-146b and IMA after treatment were all significantly decreased；after treatment，those indexes in the study were significantly lower than those in the control group（ P<0.05）. Children in both groups had a significant increase in CD3 +，CD4 +，and CD4 + / CD8 + after treatment compared with pretreatment values，and the values in the study group were significantly higher than those in the control group（ P<0.05）. Compared with what was before treatment，the expression of mir-146b and the level of IMA in the two groups of children were significantly lower after treatment，and they were significantly lower after treatment in the study group than in the control group（ P<0.05）. Conclusion:Hyperbaric oxygen combined with high-dose Vit C therapy can significantly reduce the serum levels of miR-146b and IMA in children with viral myocarditis，and improve the immune function，thus improving the clinical outcomes of children with viral myocarditis.