Objective To evaluate the value of low voltage CTCA in low body mass and low body mass index patients with low contrast media dose and radiation dose. Methods 31 patients (BM<65kg and body mass index <26kg/m2 ) were enrolled. All of patients with tube voltage and tube current tailored to BMI(BMI≤22Kg/m2 :tube voltage 80kV, tube current 400mA.22Kg/m2 ＜BMI＜26Kg/m2 : tube voltage 80kV, tube current 400mA), the flow rate and volume of contrast madia tailored to BM(BM≤55K:2.5ml/ s and 25ml, 55Kg＜BM＜60Kg: 3.0ml/s and 30ml, BM≥60Kg: 3.5ml/s and 35ml). Patients were evaluated by image quality(each coronary artery scale,attenuation,noise,SNR and CNR),contrast madia dose and radiation dose. P value below 0.05 was considered to be statistically significant. Results All patients successfully underwent low dose CTCA. The mean image quality score was 2.62±0.81. The percentage of assessable coronary artery segments was 98.21% .The mean attenuation was 411.26±72.25HU. The mean noise was 40.19±9.77HU. The mean SNR was 10.58±2.21. The mean CNR was 13.52±2.79HU.The mean effective dose was 1.28±0.39mSv.The mean contrast madia dose was 32.26±3.83ml. Conclusions Low dose CTCA may decrease the contrast media dose and radiation dose and keep image quality in patients with low body mass and body mass index.