Abstract: Objective: This study aimed to compare the effects of different scanning modes on image quality and radiation dose in thoracic aortic computed tomography angiography (CTA). Methods: The image quality and radiation dose of 30 cases of thoracic aortic CTA (Group 1, control group), 30 cases of retrospective CTA diastolic phase (Group 2) and systolic phase (Group 3), and 30 cases of wide-exposure pulse prospective electrocardiogram (ECG) (Group 4) were retrospectively analyzed. The CT value, noise, contrast-to-noise ratio (CNR), signal-to-noise ratio (SNR), and radiation dose (volume CT dose index CTDI_vol) were recorded and measured. The image quality was evaluated subjectively using the four points method. The subjective and objective indicators were analyzed statistically. Results: No differences were observed in the objective indexes of noise, CNR and SNR among the groups. The subjective score of pairwise comparison of Groups 2~4 was significantly higher than that of Group 1, and no difference was observed among Groups 2~4. The CTDI_vol values of the non-gated group (Group 1), retrospective gated groups (Groups 2 and 3), and prospective gated group (Group 4) were 13.70 (11.87,16.58), 12.62 (10.03,15.01), and 11.54 (8.92,15.56), respectively, without a statistically significant difference.