Objective To investigate the expression of serum microRNA(miR)-494 and miR-155 in chil-dren with Enterovirus type 71 hand-foot-mouth disease(EV71-HFMD),and to analyze the clinical significance of serum miR-494 and miR-155 in EV71-HFMD.Methods A total of 145 children with EV71-HFMD treated in this hospital from May 2021 to May 2023 were selected.According to the severity of the disease,they were divided into mild group(n=81)and severe group(n=64).In addition,73 healthy and disease-free children in the hospital were included in the health group.Serum expression levels of miR-494 and miR-155 as well as helper T cell 17(Th17),regulatory T cell(Treg)and Th17/Treg in the three groups were detected and com-pared.Pearson correlation analysis was used to analyze the correlation between the expression levels of serum miR-494,miR-155,Th17 and Treg,as well as Th17/Treg.The clinical data of children with EV71-HFMD were collected,and the factors influencing the severity of EV71-HFMD were analyzed by multivariate Logistic regression model.Results Compared with healthy group,serum miR-494,miR-155,Th17 and Th17/Treg in mild and severe groups were increased,and Treg were decreased(P＜0.05).Compared with mild group,ser-um miR-494,miR-155,Th17 and Th17/Treg in severe group were increased,and Treg was decreased(P＜0.05).Pearson correlation analysis showed that Th17 and Th17/Treg were positively correlated with the ex-pression levels of serum miR-494 and miR-155,while Treg was negatively correlated with the expression lev-els of serum miR-494 and miR-155(P＜0.05).The peak temperature,duration of fever ≥3 d proportion and eruption of isthmus in severe group were higher than those in mild group(P＜0.05).Multivariate Logistic re-gression results showed that the duration of fever ≥3 d,eruption in the isthmus,the high expression level of miR-494 and the high expression level of miR-155 were risk factors for severe EV71-HFMD(P＜0.05).Conclusion Se-rum miR-494 and miR-155 are abnormally elevated in children with EV71-HFMD,and the changes in their levels are closely related to Th17/Treg imbalance.Increased expression levels of serum miR-494 and miR-155 are risk factors for severe EV71-HFMD.