It is still more common to have pleural fluid in the late stage of lung cancer, which may be due to metastasis of lung cancer, that is, malignant pleural effusion. There is another situation that lung cancer has severe malnutrition, or accompanied with pneumonia, resulting in pleural effusion. As for pleural fluid extraction, it depends on the size of pleural fluid and the effect of conservative treatment, and there is no such thing as good or bad, but it is good if it can relieve the patient’s symptoms. In late stage of lung cancer, pleural fluid pumping can improve the symptoms such as chest tightness and chest pain. If the pleural effusion is malignant, the diagnosis can be confirmed by finding cancer cells through pleural fluid pumping, and then chemotherapy with thoracic cavity perfusion after the pleural fluid has been pumped, which can control the development of the disease and prolong the survival period. Inflammatory pleural effusion can also be identified, and then the patient’s symptoms can be relieved with anti-inflammatory treatment, which is also beneficial to controlling the patient’s symptoms and prolonging the survival period.