Objective To investigate the correlation between serum amyloid A(SAA)level and disease se-verity in children infected with severe acute respiratory syndrome coronavirus 2(COVID-19).Methods A to-tal of 116 children infected with COVID-19 admitted to the Department of Pediatrics of the hospital from De-cember 2022 to April 2023 were included and divided into asymptomatic/mild group and moderate/severe group according to the severity of the disease.In addition,65 healthy children who received health examination during the same period were selected as the control group.Serum SAA levels in children in acute stage and convalescent stage were detected by enzyme-linked immunosorbent assay.Results Compared with the control group,the serum SAA level in the children infected with COVID-19 was significantly increased in the acute stage(P＜0.05).The area under the receiver operating characteristic(ROC)curve(AUC)of SAA levels in the acute stage for diagnosing children with COVID-19 infection was 0.926(95％CI:0.886-0.966).In SARS-CoV-2 infected children,the SAA levels in the acute stage in the asymptomatic/mild group and the moderate/severe group were 2.71(1.29-10.86)mg/L and 37.78(18.58-92.62)mg/L,the differences were statistically significant between the two groups(Z=5.782,P＜0.001).In addition,serum SAA was pos-itively correlated with severity of SARS-CoV-2 by Spearman analysis(r=0.657,P＜0.001).Serum SAA lev-els were also significantly positively correlated with C-reactive protein(CRP),immunoglobulin(Ig)M,IgG,IgA and neutralizing antibody(NAb)in acute stage(P＜0.05).The AUC of serum SAA level in acute stage for diagnosing the moderate/severe children with SARS-CoV-2 was 0.889(95％CI:0.842-0.955),which was higher than that of CRP(P＜0.05).Compared with serum antibodies(IgM,IgG,IgA and NAb),the rate of serum SAA positive(≥5.55 mg/L)in children in acute stage was significantly higher(P＜0.05).The positive rate of serum SAA in convalescent children was significantly lower than that of serum antibody(P＜0.05).Conclusion Elevated serum SAA in acute phase is associated with increased risk of SARS-CoV-2 infec-tion and disease severity in children.Serum SAA is promising as a good biomarker for monitoring SARS-CoV-2 infection and severity in children.