Objective To explore the diagnostic value of lung ultrasound(LUS)score,computed tomo-graphy(CT)combined with serum CXC chemokine ligand 8(CXCL8)and soluble co stimulatory molecule B7-H3(sB7-H3)for severe Mycoplasma pneumoniae pneumonia(MPP)in children.Methods From April 2022 to April 2024,a total of 210 children with MPP who visited Maternal and Child Health Hospital of Zhan-gqiu District were included as research subjects,and they were separated into severe MPP group and non se-vere MPP group according to the severity of the disease.Enzyme-linked immunosorbent assay was applied to detect serum levels of CXCL8 and sB7-H3.LUS score and CT diagnosis were conducted.The value of LUS score,CT and serum CXCL8,sB7-H3 in the diagnosis of severe MPP was analyzed using the receiver operating characteristic curve.Results There were no statistically significant differences in height,age,fever days,weight,hospital stay,and gender between the severe MPP group and the non severe MPP group(P>0.05).Compared with the non severe MPP group,the serum levels of CXCL8,sB7-H3,and LUS score were all in-creased in the severe MPP group(P<0.05).The area under the curve(AUC)of LUS score,serum CXCL8,and sB7-H3 for diagnosing severe MPP was 0.865,0.785,and 0.750,respectively.The CT diagnosis results showed 35 false positives and 22 false negatives,with Kappa value of 0.459 compared to clinical examination results(P<0.05).The diagnostic results of LUS score,CT combined with serum CXCL8 and sB7-H3 showed 3 false positives and 15 false negatives,with Kappa vale of 0.828 compared to clinical examination results(P<0.05).The diagnosis of LUS score,CT combined with serum CXCL8,and sB7-H3 had higher specificity and accuracy than those of single detection of the four(P<0.05),and the sensitivity of the combined diagno-sis of the four was increased(P<0.05)and the missed diagnosis rate was reduced compared to the single de-tection of CXCL8 and sB7-H3(P<0.05).Conclusion The serum levels of CXCL8,sB7-H3,and LUS score in children with MPP increase.The specificity and accuracy of LUS score,CT combined with serum CXCL8,sB7-H3 in diagnosing severe MPP increase.