Objective To analyze the feasibility of assisted diagnosis of fetal heart volume in the screening of cardiac outflow tract lesions in single fetuses during middle and late pregnancy. Methods 190 cases of single pregnant women in mid-late pregnancy who underwent ultrasound examination in our hospital from July to October 2019,All fetuses except routine 2D echocardiography,Collect and store fetal heart volume data；Then use the fetal heart volume assistant diagnostic tool to post-process the imaging；Consistency of the two methods and repeatability within and between observers. Results 176 (92.63%) pregnant women obtained a clear image of the left and right ventricular outflow tract sections of the fetal heart using the fetal heart volume assisted diagnosis tool,Capable of measuring aortic and pulmonary inner diameters；Pearson linear correlation analysis results suggest that,The aortic and pulmonary artery diameters measured by two different ultrasound examination methods were positively correlated (both P <0.05)；Bland-Altman plot test results suggest that,The consistency of the inner diameters of the aorta and pulmonary artery measured by two different ultrasound examination methods is good,The 95% consistency limits were (-1.18 to 1.01) and (-1.81 to 1.03), respectively；In addition, fetal heart volume assisted diagnostic tools measured ICC values of aortic diameter, pulmonary artery inner diameter among observers, and within observers were all> 0.85.Conclusions The fetal heart volume assisted diagnostic tool has a good application value in the screening of cardiac outflow tract lesions in single fetuses during the second and third trimesters.