Objective To compare the quality and radiation dose of multi-slice spiral CT imaging of different dose of prospective gated axial scan for cardiac coronary artery. Methods 80 patients receiving cardiac coronary artery imaging by prospective gated axial scan were selected as the research object and were divided into two groups by the randomized double blind method with 40 cases in each group. Patients with 120kV/100mAs were included in the low dose group while with 120kV/200mAs were included in the conventional dose group. After multi-slice spiral CT scanning, the images were processed by professionals and the image quality and effective radiation dose and other indexes were compared between the two groups. Results The image quality in the low dose group: 30 cases were excellent and 10 cases were good, image quality in the conventional dose group: 31 cases were excellent and 9 cases were good and the differences between the two groups were of no statistical significance (P>0.05), The differences in SNR and CNR between the two groups were of no statistical significance (P>0.05); ED (1.71±0.18) mSv in the low dose group was significantly lower than (2.86±0.44) mSv in the conventional dose group and the difference was statistically significant (P<0.01). Conclusion The imaging quality of low dose prospective gated imaging is similar to the conventional one, but it can significantly reduce the radiation dose to the patients, which is worthy of clinical promotion