Objective:To determine miR-126 serum levels in children with congenital heart disease(CHD). Methods:A total of 54 children with CHD who received treatment in Department of Cardiology from January 2013 to June 2013 were enrolled. There were 40 children with left-right shunt acyanotic CHD(the ACHD group),including 15 children with heart failure(ACHDⅠ)and 25 children without heart failure(ACHDⅡ). There were 14 children with right-left shunt cyanotic CHD(the CCHD group)and 20 healthy children(the control group). The serum miR-126 expression level was measured to analyze the correlation between the serum miR-126 of neonates with CHD and heart failure. Results:Compared with normal controls,the expression levels of miR-126 in the ACHD group and the CCHD group were significantly down-regulated(P < 0.001). The expression levels of miR-126 in the CCHD group were significantly lower than those in the ACHD group(P < 0.05 and P < 0.001,respectively). MiR-126 expression levels were lower in the ACHDⅠ group those in the ACHDⅡ group(P < 0.001). Conclusion:The expression levels of serum miR-126 in children with CHD were significantly decreased and correlated with the severity and degree of impaired cardiac function,indicating that miR-126 may be involved in the pathological process of CHD,and it may serve as an independent evaluation indicator for the diagnosis of CHD.