The basic principle of first aid is that life comes first, and priority should be given to life-threatening diseases in the diagnosis and treatment of diseases; when there are more than one patient in need of first aid, priority should be given to patients with serious injuries; for patients with respiratory and cardiac arrest and fractures, cardiopulmonary resuscitation should be performed first, and the fractures should be treated after successful resuscitation; in the case of first aid for trauma, bleeding should be stopped first and then bandaged to prevent life-threatening hemorrhage. To pursue the smoothness of vital signs, it is inappropriate to rashly carry out examinations or operations unrelated to life safety if the vital signs are not stable, unless it is very necessary. At the same time of first aid, it is also necessary to quickly call 120 in order to get further treatment at a later stage, the following examples are given: 1. Acute myocardial infarction: Acute myocardial infarction is one of the common diseases in the emergency department, and one of the common acute fatal diseases in daily life. In the event of acute myocardial infarction, some patients will suffer from acute heart failure and respiratory distress. The primary treatment means is to open the coronary vessels, and early coronary artery interventional surgery treatment is the key to first aid, to treat myocardial infarction fundamentally, and oxygen therapy and medication are all auxiliary means; 2. Multiple trauma: multiple trauma caused by car accidents and so on, priority treatment of thoracic and abdominal cavity organ damage is the key to first aid. Because thoracic and abdominal organ injuries can easily lead to large blood loss, which can be life-threatening. Such patients may often have limb fractures or head and facial fractures, or facial skin lacerations, which are relatively less life-threatening and can be postponed. However, because limb fractures and head and facial injuries are easily detected, some patients or family members will emphasize the priority of dealing with head and facial injuries and limb fractures while neglecting the real life-threatening organ injuries, which is against the first principle of first aid. In short, only life-threatening emergencies require first aid, so the principle of first aid must be life first.