Pain under the left back rib cage can be treated in different ways according to different causes of pain. I. Pain caused by malignant tumor in the left lung base, at this time, the patient may be accompanied with coughing up blood, coughing up sputum, difficulty in breathing and other manifestations. Patients can undergo radical treatment of left lung cancer plus lymph node dissection as soon as possible after the nature of the lesion is clarified by improving lung enhancement CT. After surgery, combined with systemic chemotherapy and local radiotherapy, the residual cancer cells in the body can be killed as much as possible, and early stage patients can achieve better treatment effect. Second, the pain in the left back below the ribs caused by acute necrotizing pancreatitis. At this time, due to the massive exudation of pancreatic enzymes, it can cause necrosis of peripancreatic tissues with a large amount of exudate. Patients can be examined by CT to clarify the nature of the lesion. Active anti-infection treatment, inhibition of pancreatic enzyme secretion, large amount of fluid replenishment, reduce the exudation of the pancreas, and promote faster absorption of abdominal infection can improve the pain symptoms in the left back.