Exudative pleural effusion is relative to leaky pleural effusion. It is mainly caused by an increase in the permeability of the pleura. The increased permeability of the pleura produces a large amount of pleural fluid in the chest cavity, which is often caused by disease. A simple example, which is very common in clinical practice, is tuberculous pleural effusion. When a patient’s pleura is infected by tuberculosis bacteria and causes tuberculous pleurisy, a pleural effusion, called exudative pleural effusion, is produced. The way to distinguish exudate from leaky fluid is to draw pleural fluid and send it for laboratory tests after it is drawn out. Exudate and leaky fluid are completely different in specific gravity, pH, and cell classification. The specific gravity, pH, and cellular classification of exudate and leaky fluid are completely different. Depending on the classification and the cause of the original disease, we can distinguish whether the fluid is exudate or leaky fluid. However, the treatment of pleural fluid itself is more or less the same, which is to drain the chest cavity and release the water for decompression of the chest cavity. For example, in case of malignant pleural effusion, which is caused by pleural metastasis of lung cancer, chest drainage is also required, and after the pleural fluid is released, the pleural fluid is sent for examination and cytology, and then lung cancer treatment is carried out. After treatment, if the pleural fluid keeps producing, it will greatly affect the patient’s life. At this time, some chemotherapy drugs may be injected inside the chest cavity, which are different treatment methods. The key is to treat the primary disease, and at the same time treat the pleural fluid symptomatically, relieve the symptoms and reduce the pressure.