Choledochal cyst, also known as common bile duct dilatation, is a common biliary malformation in children and is a congenital condition. The cause is unknown and may be related to abnormal development of the pancreaticobiliary duct into the duodenal junction. There are various subtypes of the disease, and it is commonly seen as a spherical or shuttle-shaped dilatation of the common bile duct. Due to distal biliary obstruction, the child often presents with right upper abdominal pain, poor nasal function, intermittent jaundice, and in cases of large cysts, epigastric distention. In the presence of biliary tract infection, fever and even chills may occur. The time of onset of symptoms varies, with some occurring in the neonatal period and others after 3-4 years of age. Ultrasound is basically a definitive diagnosis and has the advantage of being inexpensive and convenient, while CT and MRCP (magnetic resonance biliary imaging) can further help in the staging and surgical treatment of this disease. Due to biliary obstruction, biliary stasis can occur in the liver and stones can develop in the bile duct. Even due to high bile duct pressure, bile refluxes to the pancreas and induces acute pancreatitis. The child often develops abdominal pain and jaundice, which affects the function of the liver and pancreas as well as growth and development. Therefore, once the diagnosis of choledochal cyst is clear, early surgery is recommended. With the development of surgical and anesthesia monitoring techniques, the age of the child is no longer an obstacle to treatment, and surgery in infancy has become more common. Surgery for common bile duct cyst is complicated by the removal of the gallbladder and common bile duct and the application of the jejunum instead of the bile duct, which changes the normal physiological structure. At present, the surgical method is still mainly open conventional surgery, and some medical institutions selectively adopt laparoscopic surgery, which has almost no scars on the abdomen and fast postoperative recovery, but it is still controversial and difficult to be popularized in the short term because of the technical difficulty and long operation time. Children with choledochal cysts generally recover well after surgery and can develop normally as adults. Complications such as reflux cholangitis occur in a few patients after surgery and are mostly cured by conservative treatment.