Abstract: AIM To investigate the difference of plasma miRNA expression in patients with congenital heart disease with pulmonary arterial hypertension, and to explore the correlation between expressions of PAH and plasma miRNA. METHODS 80 patients with congenital heart disease were admitted in Department of Cardiology of our hospital from February 2015 to June 2017, and were divided into three groups according to pulmonary artery pressure: 22 cases of pulmonary arterial pressure in the normal subjects (no PAH group); 37 cases of mild and moderate pulmonary hypertension (the mild and moderate PAH group); 21 cases of severe pulmonary hypertension (the severe PAH group). In addition, 20 volunteers were selected as the control group. Quantitative polymerase chain reaction (QPCR) was used to compare expression levels of plasma miR-18a, miR-27b, miR-130a and miR-204 in each group, in order to analyze the correlation between miRNA expression level and pulmonary arterial pressure. RESULTS Compared with the control group, expression levels of miR-18a, miR-27b, C group, miR-130a in the three groups increased, expression level of miR-204 decreased, and these difference were statistically significant (P<0.05); compared with the no PAH group, expression levels of miR-18a, miR-27b, miR-130a in the mild and moderate PAH group and severe PAH group increased, expression level of miR-204 was down regulated, and these difference were statistically significant (P<0.05); compared with the mild and moderate PAH group, the expression levels of miR-18a miR-27b, miR-130a in the severe PAH group increased, expression level of miR-204 decreased, and the differences were statistically significant (P<0.05). Spearman correlation analysis showed that the expression levels of plasma miR-18a, miR-27b, miR-130a were positively correlated with pulmonary arterial hypertension (r=0.845, r=0.912, r=0.933, P<0.05); expression level of plasma miR-204 was negatively correlated with pulmonary arterial hypertension (r=-0.629, P<0.05). CONCLUSION miRNA expression is different in plasma of patients with PAH secondary to congenital heart disease. The expression level of miRNA is associated with pulmonary arterial pressure.