The diagnosis of acute perforation of gastroduodenal ulcer is based on: first, clinical manifestations, the patient suddenly appears severe pain in the epigastrium, knife-like pain, ulcer perforation patients can often remember the moment when the pain suddenly occurred, and can even be specific to the time and minutes, so if the pain is like this, we should first consider the perforation of duodenal or gastric ulcer. Second, the signs, the contents of the gastroduodenal after perforation will irritate the intestine. This content is acidic and has a strong irritation to the peritoneum, so the patient’s pain is very intense, leading to a very tense state of the abdominal muscles, called platysmal abdomen, and then there is pressure pain and rebound pain. Thirdly, some auxiliary examinations, such as standing film, abdominal standing film we can see the free gas under the diaphragm, or CT can see some gas inside the abdominal cavity. Through these three points, we can usually diagnose the perforation of peptic ulcer.