Objective To analyze the application values of ultrasonic cardiogram (UCG) and dual-source CT (DSCT) in the preoperative diagnosis of congenital heart disease (CHD). Methods The clinical data of 50 cases of CHD patients treated with UCG and DSCT examinations in our hospital from January 2016 to May 2017 were retrospectively analyzed. The image features were observed, and the hemodynamic parameters measured by UCG and DSCT [aortic root diameter (AORD), left atrial diameter (LAD), left ventricular end diastolic diameter (LVDD), left ventricular end systolic diameter (LVDS), left ventricular ejection fraction (LVEF)] and the end systolic image parameters [left pulmonary artery diameter (LPA), right pulmonary artery diameter (RPA), diaphragmatic level reduced aortic diameter (DAO) and the McGoon ratio] were compared. And the diagnostic accuracy of UCG, DSCT and UCG+DSCT was analyzed based on the results of surgery. Results There was no significant difference in the AORD, LAD, LVDD, LVDS, LVEF and DAO measured by UCG and DSCT (P>0.05), but the LPA, RPA and McGoon ratio at DSCT end-systole were greater than those by UCG (P<0.01). There was no statistically significant difference in the accuracy in the diagnosis of cardiac part, and the linking part between the heart and large blood vessel by any two of UCG, DSCT and UCG+DSCT (P>0.05). The accuracy in the diagnosis of large blood vessel was 90.08% by DSCT and 96.16% by UCG+DSCT, which was higher than that by UCG with 73.08% (P<0.05). The overall diagnostic accuracy with 95.56% by UCG+DSCT was higher than that by UCG with 89.24% and by DSCT with 91.77 % (P<0.05). Conclusion UCG and DSCT have certain value in the preoperative diagnosis of CHD. The latter one has higher diagnostic accuracy than the former one in the diagnosis of large blood vessels, and the combination of the two can be helpful for the comprehensive and accurate diagnosis and is worthy of clinical promotion and practice.