Abstract: Objective: To explore the applicative value of low tube voltage and low concentration contrast agent bronchial artery(BA) CTA under retrospective ECG gating. Methods: 120 patients with hemoptysis were randomly divided into conventional dose group(group A) and double low dose group(group B), 60 cases in each group. Both groups underwent enhanced arterial phase scanning. The tube voltage was 120 kV and the concentration of contrast medium was 350 mgI/mL in group A, while the tube voltage was 80 k V and the concentration of contrast medium was 270 mgI/mL in group B. The CTA images were reconstructed after scanning, and the differences of BA display rate, image quality, and radiation dose and iodine intake between the 2 groups were analyzed respectively. Results: 115 cases completed scan successfully in the 2 groups(57 cases in group A and 58 cases in group B). The display rate of BA in group B was higher than that of group A(P<0.05); The excellent rate and qualified rate of image, noise, CT value, SNR and CNR of BA in group B were higher than those of group A(P<0.05); CTDI_vol, DLP, ED and iodine intake in group B were lower than those of group A(P<0.05). Conclusion: Low tube voltage and low concentration contrast agent combined with retrospective ECG gating show important value in BA-CTA, image quality can be improved, the radiation dose and iodine intake can be reduced obviously.