Abstract: Objective: To evaluate the potential of acquiring the diagnostic images of coronary CT angiography with prospective ECG-triggered high pitch flash spiral acquisition in 100 kV tube voltage combined with iterative reconstruction and contrast of iodixanol(270 mgI/mL). Methods: The 60 patients were divided into A and B two groups randomly, whose heart rate ≤ 70 /min. In the A group, their coronary CT angiography images were collected with prospective ECG-triggered high pitch flash spiral mode in 100 kV tube voltage combined with iterative reconstruction(convolution kernel B26f) and contrast of iodixanol(270 mgI/mL). In the B group, their coronary CT angiography images were collected with prospective ECG-triggered sequence mode in 120 kV tube voltage combined with filtered back projection(convolution kernel B26f) and contrast of iopromide(370 mgI/mL). The image quality and effective radiation dose of two groups were assessed. Results:(1) There were no significant differences in age, heart rate and BMI between the two groups.(2) Image qualities: There were no significant differences in the subjective image quality evaluation between the two groups.In objective image quality assessment, in addition to the left coronary artery of SD and SNR numerical difference was statistically significant, no statistically significant difference were observed in the other indicators.(3) Radiation dose: The average effective radiation dose was(0.94 ±0.05)mSv in group A and(4.31 ±1.21) mSv in group B respectively. The differences between the two groups have statistical significance. In effective dose group A decreased sharply than group B by about 78.2%. Conclusions: In coronary CT angiography with prospective ECG-triggered high pitch flash spiral acquisition in 100 kV tube voltage combined with iterative reconstruction and contrast of iodixanol(270 mgI/mL) which image quality can meet the demand of clinical diagnosis, it compared with prospective ECG-triggered sequence mode in 120 kV tube voltage, could decrease the effective dose by about 78.2%.