Abstract: 　Objective　To evaluate the application of dual-source CT (DSCT) using low-dose technology in diagnosing complex congenital heart diseases. Methods The DSCT data of 31 cases with complex congenital heart diseases confirmed by operation were retrospectively analysed and classified into four groups: group A(≤4 months old, n=12); group B (>4 months old~1 year old, n=3); group C (>1 year~6 years old, n=8) and group D (>6 years old, n=8). Results The diagnosis conformation rate of DSCT with surgery were 94.59% . The diagnostic conformation rate of intracardic anormalies using DSCT was 92.86%. And the diagnostic conformation of DSCT in patients with abnormal connection of atrium or ventricle to great vessels and the extrocardic anormalies was 95.65%. The average effective dose in each group were 1.16±0.06 mSv, 1.28±0.07 mSv, 1.96±0.54 mSv and 2.77±0.38 mSv, respectively. The ratio of the high quality images was 90.32%. Conclusions The application of low dose technology in DSCT can clearly display the anomalies, and significantly reduce the radiation dose without losing image quality as well.