The aim of this study was to assess the effect of exposure factors such as kVp and mA applied by BMI on the image quality and patients absorbed dose of Coronary angiography in CT. Each data sets were into 4groups with different exposure values : Group A at 100kVp, 240mAs, Group B at 120kVp, 240mAs, Group C at 100kVp, 270mAs and Group D at 120kVp, 270mAs, and the mean of the scores of 4 groups was calculated for image quality as 4grades that is, 1(poor), 2(fair), 3(good) and 4(very good). Patient absorbed dose was calculated as DLP on the monitor. In case of absorbed dose, deviation in 2groups at 100kVp was 5.6 mGy·cm, 11 mGy·cm was at 120kVp(DLP) with p<0.05. There was rather difference between groups with 100kVp or 120kVp respectively but the gaps were very little. No significant correlation was found between exposure factors and image quality in any images assessed(p>0.05), and the image quality was sufficient for diagnosis. As we applying coronary angiography, the selection of adequate exposure factors considering BMI identified might be effective for reduction of patient absorbed dose, improvement of image quality and diagnostic accuracy.