”Dilatation of the common bile duct”, is one of the most common congenital biliary malformations in clinical practice. Its lesion mainly refers to such a congenital malformation in which a part of the common bile duct is cystic or shuttle-shaped dilated, sometimes accompanied by dilatation of the intrahepatic bile duct. The specific cause is an anatomical variation of the bile duct and pancreatic duct, resulting in abnormal pancreaticobiliary flow, bile reflux into the pancreatic duct and pancreatic juice into the bile duct, causing recurrent cholangitis and pancreatitis, resulting in frequent abdominal pain in children, and in severe cases, purulent cholangitis and necrotizing pancreatitis, which can endanger the life of children. This disease, if left untreated, can cause secondary biliary stasis, resulting in biliary stones and biliary obstruction, aggravating biliary infection and causing biliary cirrhosis of the liver. The yellow sclera and skin of the child is due to biliary obstruction. Through anti-inflammatory treatment, some of the obstructed bile ducts can be restored, but some of them cannot be restored and only emergency surgery can solve the problem. If the child has severe biliary cirrhosis, finally only a liver transplant can save the child’s life. In addition, long-term inflammatory stimulation of choledochal cysts can lead to rupture of the cysts, especially cystic choledochal cysts, causing biliary peritonitis and endangering the child’s life; on the other hand, biliary tract cancer can occur, and recent studies have found that biliary tract cancer has become the most serious complication of congenital bile duct dilatation. The incidence of biliary tract carcinoma in congenital bile duct dilatation is reported to be 25-40 times higher than that in the normal population. The rate of biliary tract carcinoma also increases dramatically with age. Especially for some children with small cysts, the cysts can be detected by ultrasound when the child has abdominal pain, and after the abdominal pain disappears, the cysts are obviously shrunken or even disappeared by ultrasound, such children should be closely observed and operated in time, and parents are reminded that such patients are at high risk for bile duct cancer. The diagnosis of choledochal cyst is very easy and can be confirmed by ultrasound. Therefore, parents of children with recurrent abdominal pain should take their children for a routine biliary ultrasound to prevent missing the child’s disease and thus delaying treatment. For the treatment of congenital bile duct dilatation, in principle, surgery should be performed promptly after the diagnosis is clear. The classical procedure for radical choledochal cyst treatment is: gallbladder, choledochal cyst excision + Roux-Y anastomosis of jejunohepatic duct. Currently there are two options for this procedure: traditional open surgery and laparoscopic surgery. Choledochal cyst surgery is a difficult surgery in the field of pediatric surgery because the common bile duct is adjacent to the hepatic artery, gastroduodenal artery, portal vein, duodenum, pancreas and other important vessels and organs, and damage to any of these tissues can lead to poor postoperative recovery and even serious complications. Moreover, choledochal cysts contain a rich vascular network, which usually involves some intraoperative bleeding and requires proper postoperative blood transfusion for recovery. Therefore, this surgery requires a high level of human anatomy and surgical techniques from the surgeon in charge. At the same time, the traditional open surgery method is very disturbing and traumatic to the abdominal organs of the child, and the postoperative pain of the child is heavy and the recovery is slow. Laparoscopic choledochal cyst surgery is performed through laparoscopic equipment, which greatly increases the difficulty of the operation and places higher demands on the technical level of the surgeon in charge, making it difficult for most hospitals to perform this procedure. However, through this fine surgical operation, there is less interference with the abdominal organs of the child, and due to the magnification of the imaging system, the anatomy is clear, hemostasis is better, intraoperative bleeding is minimal, and in general, no blood transfusion is needed during and after the operation, and the child’s postoperative pain is significantly reduced and recovery is significantly accelerated, with many significant advantages such as light trauma, less pain, faster recovery and shorter hospitalization. At the same time, this procedure leaves only four small holes in the abdominal wall and no obvious scars after healing, which is especially important for female children.