As a surgical procedure, tooth extraction may cause some complications during and after surgery, among which infection and subcutaneous emphysema are some of the more painful postoperative complications that may cause patients. In this paper, we address the causes of subcutaneous emphysema after extraction with the aim of providing clinical reference to avoid or reduce the occurrence of such complications. This pathology is caused by the rupture of the cervical air sac or subclavian air sac due to improper management and rough catching, or by the spillage of gas under the skin due to the puncture of the air sac by other sharp objects, resulting in subcutaneous emphysema. In addition, the gas can also escape into the subcutis due to the fracture of bones with gas cavity such as humerus, urochondrium and sternum. Subcutaneous emphysema of the chest wall is usually secondary to sternal and/or rib fractures with pneumothorax, especially in patients with multiple rib fractures with tension pneumothorax, and can also be complicated by tracheal, bronchial, pulmonary and esophageal injuries. Occasionally, it is seen secondary to endoscopic injury. There are usually three ways for air to enter the subcutaneous tissue through the damaged area: 1.When the pneumothorax is accompanied by wall pleura damage, the air in the chest cavity can enter the subcutaneous tissue of the chest wall through the damaged area; 2.When the trachea, bronchus or esophagus is ruptured, the air can enter the mediastinum directly through the rupture, and then diffuse to the neck, face and subcutaneous tissues of the chest; 3, air enters subcutaneous tissues directly through the body surface wound of the chest wall.