Objective To evaluate the image quality and radiation dose of 320-slice volume CT coronary angiography (CCTA) in patients with large body weight using low radiation and low contrast agent dosage. Methods 86 patients with coronary heart disease and weight 90Kg were randomly divided into experimental group B and control group A. A group, 44 cases, using 120Kv tube voltage, 320mgI/ml contrast agent ioversol, group B, 42 cases, using 100Kv tube voltage, Visipaque 270mgI/ml contrast agent. A, B two groups using the intelligent Ma technology, contrast agent dosage was 0.625ml/Kg, using Toshiba Aquilion One prospective ECG gated scanning, 3D adaptive iterative reconstruction algorithm (3D AIDR) and noise reduction. The aortic root were measured, left main (LM), left anterior descending (LAD), left circumflex and right coronary artery (LCX) (RCA) CT enhancement value between groups were compared between the two groups at the same time, noise (SR), contrast to noise ratio (CNR), effective radiation dose (ED), statistical analysis. Results A, B two groups of image in the vessels of CT showed no significant difference (P>0.2 for all B), group ED: (3.68±2.19)mSv than in the A group: (8.16±5.55)mSv (P<0.05), decreased by 54%. Conclusion Low dose radiation and low contrast (double low) technique for image quality may be obtained in conventional radiation and contrast agent under the condition of general weight patients, to reduce the X-ray and iodine contrast agent brings harm to the patients.