Pulmonary effusion is the accumulation of fluid in the pleural cavity, the causes of which are mainly due to inflammation, tumor, tuberculous causes, or injury to cardiopulmonary blood vessels; treatment may require surgical resection of the lesion, puncture and aspiration of fluid, anti-inflammatory and anti-tuberculous treatments, and other methods. Under normal circumstances, the human thoracic cavity consists of visceral pleura and wall pleura to form the pleural cavity, and pleural exudation and absorption will form a dynamic balance, but due to the stimulation of inflammation, tumor, tuberculosis or damage to cardiopulmonary blood vessels lead to excessive production of fluid in the thoracic cavity, which can not be absorbed quickly, and thus lead to pleural effusion. The treatment of pleural effusion varies according to the amount of fluid and the cause of the disease. Basic evacuation of the fluid or continuous closed pleural drainage can relieve the symptoms. Further treatment for pleural effusion depends on the cause of the disease, such as tumor or pyothorax, pleurisy, etc. Surgical resection of the diseased area may be required, as well as antitumor, anti-inflammatory, and anti-tuberculosis treatments.