OBJECTIVE： To investigate the effect of preoperative use of high-dose simvastatin on the pulmonary artery pressure in congenital heart disease with left-to-right shunt. METHODS： 86 patients with left-to-right shunt congenital heart disease who were planned to implement interventional occlusion therapy were randomly divided into control group（43 cases） and observation group（43 cases）. Patients in both groups were given digitalis，diuretics，anticoagulants and other basic treatments； On this basis，control group received Sildenafil citrate tablet， 25 mg， 3 times a day， orally given 1 h before a meal； observation group received Simvastatin tablet 80 mg， once every evening， orally. The treatment course for both groups was 7 d. Mean pulmonary hypertension （mPAP）， N terminal prohormone brain natriuretic peptide （NT-proBNP）， arterial oxygen saturation （SaO2）， arterial oxygen tension （PaO2）， pulmonary blood circulation ratio （Qq/Qs）， pulmonary pressure variation （Rp/Rs）， pulmonary vascular resistance index （PVRi） before and after treatment in 2 groups were observed， and related indicators of liver functions [alanine aminotransferase （ALT）， aspartate aminotransferase（AST）] and myocardial enzymes [lactate dehydrogenase （LDH）， creatine kinase MB（CKMB）] were detected. The incidence of adverse reactions were deteted. RESULTS： Before treatment， there were no significant differences in mPAP， NT-proBNP， SaO2，PaO2， Qq/Qs， Rp/Rs， PVRi， ALT， AST， LDH and CKMB levels in 2 groups （P＞0.05）. After treatment， mPAP， NT-proBNP， Rp/Rs and PVRi levels were significantly lower than before， SaO2， PaO2， and Qq/Qs levels were significantly higher than before and Qq/Qs level in observation group was higher than these in control group.The difference was statistically significant （P＜0.05）. There was 1 patient showed severe liver injury in observation group and exited the test； the other 85 patients showed no obvious adverse reactions， with successful surgery and good prognosis. CONCLUSIONS： The preoperative use of high-dose simvastatin shows obvious effect on controlling mean pulmonary hypertension， reducing mPAP， NT-proBNP， Rp/Rs and PVRi levels and increasing SaO2， PaO2， and Qq/Qs levels before operation， with good safety.