Abstract: Objective:To evaluate the value of low-dose scanning with 128-slice CT coronary artery angiography. Methods:120 patients, heart rate<80 bpm, regular rhythm, were randomly divided into two groups. The first group was 60 patients with low-dose (100 kV) scanning, the second group was 60 patients with conventional dose (120 kV) scanning. Volume computed tomography dose index (CTDIvol) and dose-length product (DLP) were automatically obtained by CT scanning, and effective dose (ED) were obtained by calculating. Two associate chief physicians review the CT images independently. Two groups were evaluated for image quality score (10 segments, each coronary artery segment, 4-point scale) and radiation dose, A p value below 0.05 was considered statistically significant. Results:The mean CTDIvol for the first group was 11.35 mGy ±1.2 mGy, the mean ED was 2.62 mSv ±1.4 mSv, and the mean CTDIvol for the second group was 22.82 mGy ±2.3 mGy, the mean ED was 5.27 mSv ±2.0 mSv, The ratio of CTDIvol and DLP for two groups were 49.7%, 49.7% respectively, the two groups difference were statistically significant (P<0.05).The mean image quality score for two groups were not statistically significant (P>0.05). Conclusion:Low-dose scanning of 128-slice spiral CT can maintain highest image quality while reducing the radiation dose (100 kV) in coronary artery angiography. This technique is suitable for promote in clinical.