Abstract: Objective: To investigate the optimal dosage of contrast agent in three-dimensional dynamic enhanced magnetic resonance angiography (3D CE-MRA) in the imaging of arterial lesions of both lower limbs. Methods: 45 patients who underwent 3D CE-MRA angiography of lower extremity arteries in our hospital were randomly divided into three groups A, B and C. The gadolinium dosages of the three groups were respectively 0.1 mmol/kg, 0.2 mmol/kg and 0.3 mmol/kg. They were injected intravenously with saline at the ratio of 1:1. The images of different dose scanning schemes were scored subjectively and objectively. Subjective scoring: the lower limb arteries were divided into femoral artery, popliteal artery and calf artery (posterior tibial artery, anterior tibial artery and common peroneal artery). The quality of MIP reconstruction images was evaluated, and the overall venous overlap scoring of calf and foot vessels was also carried out. Finally, the differences of the three scanning schemes were compared by Wilcoxon test.The objective scoring is to measure and calculate the signal intensity Si, signal-to-noise ratio SNR and contrast-to-noise ratio of the original enhanced images of the three groups, compare the horizontal signal intensity differences of femoral artery, popliteal artery and calf artery, and compare the differences of the three scanning schemes by t-test. Results: When the contrast medium dosage was 0.1 mmol/kg, the image quality scores of femoral artery, popliteal artery and calf artery were (3.35±0.25), (2.97±0.25), (2.35±1.15) respectively; When the dosage of contrast agent was 0.2 mmol/kg, the scores of the above parts were (3.75±0.35), (3.55±0.32), (2.97±0.70) respectively; When the dosage of contrast agent was 0.3 mmol/kg, the scores of the above parts were (3.90±0.41), (3.83±0.52), (3.10±0.75) respectively. 33.33% of the images in group A did not meet the diagnostic needs, while all the images in group B and C met the diagnostic needs. There was significant difference between group A and group B, and there was no significant difference between group B and group C. B The Si, SNR and CNR of femoral artery and popliteal artery in group C were significantly higher than those in group A, and there was no significant difference between group B and C. The images of group B and C were better than those of group A. Conclusion: Appropriate increase of the contrast medium dosage is helpful to improve the 3D CE-MRA imaging quality of both lower limb arteries. The contrast medium dosage of 0.2 mmol/kg is reliable and accurate for the evaluation of blood vessels, and can provide accurate and reliable imaging basis for the formulation of treatment plan for patients with peripheral artery diseases.