Abstract: Objective: To evaluate the value of double low-dose CT coronary angiography (CTCA) by single cardiac cycle acquisition with 320-detector row CT. Methods: 51 patients with low heart rate and normal body type enrolled this study from October 2017 to January 2018. All patients were divided into two groups (Group A and Group B). Group A included 25 patients with tube voltage 80 kV and tube current tailored to body mass index (BMI) (300-500 mA), the injection rate and volume of contrast agent (20-30 mL) tailored to body mass (BM). Group B included 26 patients with tube voltage 100 kV and tube current tailored to BMI (300-500 mA), the injection rate and volume of contrast agent (35-45 mL) tailored to BM. Two groups were evaluated by contrast agent, radiation dose and image quality. P values below 0.05 were considered to be statistically significant. Results: All patients successfully underwent single cardiac cycle CTCA. The mean contrast agent for group A was 28.20 mL; this represents a 30% reduction as compared with that group B (mean, 45.58 mL; t=-9.935, P<0.001). The mean effective dose for group A was 0.96 mSv; this represents a 45% reduction as compared with that group B (mean, 1.76 mSv; t=-10.412, P<0.001). The mean image quality score was 3.59±0.58 obtained with Group A versus 3.66±0.53 obtained with Group B (Z=-1.618, P=0.106). The mean CNR was 20.26±7.34 obtained with Group A versus 23.29±7.06 obtained with Group B (t=-3.350, P=0.001). Conclusion: Double low dose CTCA may decrease the contrast agent and radiation dose keeping image quality assessable in specify patients.