Abstract： Objective:To explore the value of serum miR-155-5p(miR-155-5p)and miR-126(miR-126)in evaluating the severity of acute respiratory distress syndrome(ARDS)in children.Methods:This study was a retrospective cohort study, a total of 114 children with ARDS admitted to the PICU of Zaozhuang Maternal and Child Health Hospital from May 2017 to November 2020 were selected as the ARDS group, 54 males and 60 females, aged(6.23±1.05)years old, ranging from 4 to 8 years old.The children were divided into mild group( n=38), moderate group( n=44)and severe group( n=32)according to oxygenation index.At the same time, 112 children undergoing physical examination at the same time were selected as the healthy group, 55 males and 57 females, aged(6.19±1.11)years old, ranging from 4 to 8 years old.The serum miR-155-5p, miR-126 and PaO 2/FiO 2 values of the four groups of children were compared.The correlation between miR-155-5p, miR-126 and oxygenation index of children in the ARDS group was analyzed.At the same time, the ROC curve of subjects was drawn to analyze the predictive value of miR-155-5p and miR-126 for the severity of the disease in children in the ARDS group. Results:The levels of serum miR-155-5p and miR-126 in mild group, moderate group and severe group were higher than those in healthy group, and the PaO 2/FiO 2 values were lower than those in healthy group, the differences were statistically significant( P<0.05).The serum miR-155-5p and miR-126 levels in the moderate and severe groups were significantly higher than those in the mild group, and PaO 2/FiO 2 values were significantly lower than those in the mild group, with a statistically significant difference( P<0.05).The serum miR-155-5p and miR-126 levels in severe group were significantly higher than those in moderate group, and PaO 2/FiO 2 values were significantly lower than those in moderate group, with statistical significance( P<0.05).MiR-155-5p and miR-126 were negatively correlated with PaO 2/FiO 2 in children, and the difference was statistically significant( P<0.05).The sensitivity and specificity of miR-155-5p were 78.9% and 83.9% respectively in predicting the severity of the disease, the sensitivity and specificity of miR-126 were 66.7% and 86.6% respectively, the sensitivity and specificity of the two methods were 96.5% and 94.2% respectively, the sensitivity and specificity of miR-155-5p combined with miR-126 in the diagnosis of ARDS were significantly higher than those of a single test, the differences were statistically significant( P<0.05). Conclusions:Serum miR-155-5p and miR-126 play an important role in the occurrence and development of ARDS, and have obvious correlation with the severity of children.The combined detection of miR-155-5p and miR-126 can effectively improve the prediction sensitivity and specificity.