To identify the effects of the application of the adaptive statistical iterative reconstruction (ASIR) technique in combination with the other two factors of body mass Index (BMI) and tube potential on radiation dose in cardiac CT. The patient receiving operation the cardiac CT examination was divided four groups into according to kVp.[A group(n=20), Non-ASIR, BMI < 25, 100 kVp; B group(n=20), Non-ASIR, BMI > 25, 120 kVp; C group(n=20), 40% ASIR BMI < 25, 100 kVp; D group(n=20), 40% ASIR, BMI > 25, 120 kVp] After setting up the region of interest in the main artery central part and right coronary artery and left anterior descending artery, the CT number was measured and an average and standard deviation were analyzed. There were A group and the difference which the image noise notes statistically between C. And A group was high so that the noise could note than C group (group A, 494 ${pm}$ 32 HU; group C, 482 ${pm}$ 48 HU: P<0.05) In addition, there were B group and the difference noted statistically between D. And B group was high so that the noise could note than D group (group B, 510 ${pm}$ 45 HU; group D, 480 ${pm}$ 82 HU: P<0.05). In the qualitative analysis of an image, there was no difference (p>0.05) which a group, B group, C group, and D as to average, A group 4.13${pm}$0.2, B group 4.18${pm}$0.1, and C group 4.1${pm}$0.2 and D group note statistically altogether with 4.15${pm}$0.1 as a result of making the clinical evaluation according to the coronary artery segments. And the inappropriate image was shown to the diagnosis in all groups. As to the radiation dose, a group 8.6${pm}$0.9 and B group 14.9${pm}$0.4 and C group 5.8${pm}$0.5 and D group are 10.1${pm}$0.6 mSv.