Objective To evaluate a self-designed in-situ fenestration system to preserve left subclavian artery during thoracic endovascular aortic repair (TEVAR).Methods From June 2016 to May 2017,aortic dilatation disease patients with insufficient proximal landing zone were treated by the selfdesigned in situ fenestration system to preserve the left subclavian artery during TEVAR.The patients were regularly followed-up with CTA.Results Totally 12 patients with an average age of 65 ± 11 years were enrolled.Among them,6 patients had thoracic aortic aneurysm and the other 6 suffered from aortic dissection.The mean operating time was 145 ± 36 minutes.The perioperative procedure success rate was 100％.One patient had intraoperative type Ⅰ endoleak,1 patient had type Ⅱ endoleak.One patient had suffered from stroke and 1 patient had mild paraplegia post-operatively.All patients were followed-up for a mean time of 6.5 ± 3.0 months.The type Ⅰ endoleak in 1 patient disappeared,type Ⅱ endoleak remained in one.There was no death during perioperative and in follow up period.Conclusions This self-designed in-situ fenestration system effectively and quickly restores the blood flow of the left subclavian artery during TEVAR.