Closed thoracic drainage is one of the operations that physicians must master and use frequently. It has an important role in maintaining the negative pressure in the pleural cavity of the resuscitated lung and in maintaining the cardiac return of blood. The main purposes of closed thoracic drainage are: i. Application in case of pneumothorax, mainly for more severe pneumothorax and tension pneumothorax. Closed thoracic drainage can promote lung reopening and maintain the negative pressure state in the pleural cavity. Second, to promote the drainage of fluid in the pleural cavity, mainly for infection, tuberculosis, tumors, poor cardiac function, liver cirrhosis and connective tissue disease and other conditions caused by the drainage of fluid in the chest cavity of medium degree or above, can reduce the pressure on the lungs and heart and other organs, reduce the symptoms. Third, chest trauma. The need for continuous drainage of fluid accumulation in the pleural cavity after thoracic surgery and cardiac surgery.