Abstract: Objective To investigate the accuracy of pulmonary arterial systolic pressure（PASP）estimated by Doppler echocardiography in patients with Eisenmenger syndrome. Methods This was a retrospective and observational study. The datum of 72 cases of hospitalized patients diagnosed with Eisenmenger syndrome between January 2010 and December 2014 were collected by reviewing medical records. All patients underwent Doppler echocardiography examination within 72 hours before right heart catheterization. By comparing with the PASP determined by right heart catheterization,the accuracy of the PASP estimated by Doppler echocardiography was evaluated.Results There was a significant difference between the PASP determined by right heart catheterization and the PASP estimated by echocardiography（109.8±28.2）vs（100.6±25.4）mm Hg,P=0.003. Pearson correlation analysis showed that there was a moderate correlation between PASP determined by the right heart catheterization and estimated by echocardiography（r=0.57,P＜0.01）. Based on Bland-Altman analysis,the mean difference between the PASP estimated by echocardiography and determined by right heart catheterization was-9.2mm Hg（95% CI-58.2to 39.8mm Hg）. Compared to right heart catheterization,Doppler echocardiography over-estimated PASP by 10 mm Hg in 14cases（19.4%）and underestimated PASP about 10 mm Hg in 32cases（44.4%）.There was a significant difference in underestimation rate between patients with pre-tricuspid bypass（atrial septal defect,25.0%）and with post-tricuspid bypass（ventricular septal defect and patent ductus arteriosus,56.8%,P=0.008）. Conclusion Doppler echocardiography had some certain limitations in the estimation of PASP in patients with Eisenmenger syndrome. Doppler echocardiography may be more likely to underestimate PASP in patients with post-tricuspid bypass.