The purpose of emergency care is to take rapid and effective treatment methods at the early stage of injury or morbidity to save life, control deterioration, protect organ function and obtain a good clinical prognosis as soon as possible. Emergency care is not a separate job or a single concept, but is known as emergency medicine in the sequence of clinical medical specialties. The emergency medical service system based on emergency medicine in China includes three modes: pre-hospital emergency, in-hospital emergency and critical care. 1. pre-hospital emergency: before arriving at the hospital, emergency personnel provide on-site life support and emergency treatment for acute and trauma patients, including rapid stabilization and safe transfer. 2. in-hospital emergency: it is the most important and complex central part of the emergency service system, mainly undertaken by the emergency department of the hospital. It provides support and guarantee for patients to obtain timely follow-up specialized medical services; 3.Critical care: for critically ill patients with serious injuries and diseases, they need to be monitored and treated in the emergency resuscitation area or observation area. Depending on the condition, they may be admitted to the emergency intensive care unit for life and organ function support. Such patients usually have unstable vital signs, are in critical condition, are not suitable for moving or transporting, or can be cured in a short period of time without further hospitalization.