ObjectiveTo determine the influence of proximal aneurysm neck anatomy on typeⅠA endoleak follo-wing endovascular aortic aneurysm repair (EVAR) for infrarenal abdominal aortic aneurysm. MethodsFrom September 2007 to February 2014, 111 consecutive patients with non-ruptured abdominal aortic aneurysms were treated with EVAR. The preoperative CTA of abdominal aortic was obtained by every patient, and the three-dimensional imaging was reconstructed and measured by software of Osorix. Then, the relation between the recurrence of typeⅠA endoleak and the concerned data measured by Osorix was analyzed by the statistical software. ResultsThe recurrence of typeⅠA endo-leak was related to the proximal neck angle of the abdominal aortic aneurysm, which weren't related to the proximal neck diameter and variation rates, the mural thrombas and calcification rate, and the maximum diameter of abdominal aortic aneurysm by multivariate analysis. ConclusionsThe complicated proximal aneurysm neck anatomy is a major cause for the typeⅠA endoleak, the proximal neck angle of the abdominal aortic aneurysm is the independent factor. The applica-tion of EVAR depends largely on the shape of the proximal aneurysm neck.