Objective: To evaluate the application of echocardiography in diagnosis of pediatric pulmonary artery sling. Methods: Twenty-five children diagnosed as pulmonary artery sling in the Children's Hospital, Zhejiang University School of Medicine from July 2012 to August 2017, and 50 healthy children(control group) were enrolled in the study. Echocardiography was performed in all subjects. The origins of the left pulmonary artery(LPA) and right pulmonary artery(RPA) were observed; the internal diameters of LPA, RPA and main pulmonary artery(MPA) were measured; and the ratios of LPA/MPA and RPA/MPA were calculated. The value of RPA/MPA and LPA/MPA in diagnosing pulmonary artery sling was evaluated by ROC curve. Results: Echocardiography showed that the internal diameters of RPA were increased in all patients; while the LPA and blood flow signals in common pulmonary arterial bifurcation were not found in 24 cases, in whom the MPA was directly extended to the RPA, and the LPA was from the massive RPA. The ultrasound of one special case showed that there was no distinct bifurcation of MPA; the MPA walked to the right and then to the left with no change in the internal diameter. There were significant differences in RPA/MPA(0.50±0.05 vs. 0.71±0.15, t=7.06, P < 0.01) and LPA/MPA(0.52±0.05 vs. 0.39±0.09, t=6.94, P < 0.01) between controls and the patients. ROC curve analysis showed that the AUC of RPA/MPA and LPA/MPA in diagnosis of pulmonary artery sling were 0.90 and 0.89, respectively. When taking 0.60 as the cutoff value, the sensitivity, specificity, positive predictive value, negative predictive value and accuracy of RPA/MPA in diagnosis of pulmonary artery sling were 79%, 100%, 100%, 91% and 93%, respectively. When taking 0.43 as the cutoff value, the sensitivity, specificity, positive predictive value, negative predictive value and accuracy of LPA/MPA in diagnosis of pulmonary artery sling were 71%, 96%, 89%, 87% and 88%, respectively. Conclusions: Echocardiography can effectively diagnose pediatric pulmonary artery sling. The RPA/MPA ratio of 0.60 and the LPA/MPA ratio of 0.43 can be used as cutoff values for diagnosis.