Objective To investigate effects of complete resection of the cyst or incomplete resection with 3 ～ 5 mm remnant proximal cyst wall in treating adult type Ⅰ choledochal cyst (CC).Methods Medical records of 133 surgical patients with type Ⅰ CC from December 1995 to December 2017 in the First Affiliated Hospital of Zhengzhou University were reviewed retrospectively.According to whether to reserve the 3 ～ 5 mm cyst wall in proximal end of cyst,133 patients were divided into unreserved group (n =85) and reserved group (n=48),and the related indicators of the two groups were compared and analyzed.Results No significant difference was observed in age,sex ratio,clinical performance between the two groups(all P＞0.05).And there was no statistical difference in the operation time,intraoperative blood loss,and biliary-intestinal anastomosis diameter between the two groups(all P＞0.05).The main complications of the two groups were similar,including incision and abdominal infection,bile leakage,cholangitis,reflux cholangitis,bile duct stones and anastomotic stricture,and there was no statistical difference in the incidence of each complication.Biliary-intestinal anatomical site malignancy was observed in one patient with recurrent cholangitis in the reserved group in the 33th months.Conclusions There was no statistical difference in the incidence of early and late complications in two different methods of cyst management for treating adult type Ⅰ CC.Whether reserve the 3～5 mm cyst wall in proximal end of CC increases the risk of cancer still needs further studies.