Abstract: Objectives To explore the relationship of serum miR-30a and cardiac function in children with congenital heart disease (CHD), and the diagnostic value of serum miR-30a to heart failure. Methods From January 2013 to June 2013, 65 children with CHD were enrolled, and divided into the HF group (patients with heart failure, n=40) and the Non-HF group (patients without heart failure, n=25) according to modified Ross score. The serum miR-30a expression level was quantified by real-time PCR. Left ventricular ejection fraction (LVEF) was tested by echocardiography. The correlation between miR-30a and modified Ross score and LVEF were evaluated with Spearman's analysis. The area under the receiver-operating characteristic (ROC) curve for miR-30a was examined. Results The expression level of miR-30a in HF group was higher than that in Non-HF group, the LVEF was lower in HF group than that in Non-HF group (all P<0.001). The serum miR-30a level was positively correlated with modified Ross score (r=0.63, P<0.01) and negatively correlated with LVEF (r=-0.32, P<0.01). According to ROC analysis, the AUC of miR-30a for detection of HF was 0.7440. Conclusion The expression level of serum miR-30a was closely correlated with the cardiac function, which can be as a biomarker for indicating the heart failure in CHD.