There are more reasons leading to postoperative pleural effusion of lung cancer, which are commonly found in postoperative trauma blood seepage, postoperative celiac disease, postoperative thoracic cavity infection resulting in pyothorax, postoperative generalized hypoproteinemia and so on. Postoperative pleural effusion after lung cancer surgery is a relatively common phenomenon, which usually refers to the accumulation of fluid in the pleural cavity after surgery, and patients usually have symptoms such as chest tightness, shortness of breath and dyspnea. When the pleural fluid is small, it can be gradually absorbed in about two weeks and usually does not need special treatment. If the pleural effusion is more and causes obvious clinical symptoms, then closed drainage of chest cavity and symptomatic supportive treatment according to the situation are needed. Therefore, the specific causes of postoperative pleural effusion of lung cancer need to be analyzed on a case-by-case basis.