The best emergency time for sudden death is immediate in-place resuscitation, preferably within 5 minutes, more than 5 minutes may result in irreversible damage, and the probability of successful resuscitation beyond 10 minutes is very low. Sudden death is a sudden death without any aura, generally without any life-threatening pre-existing manifestations or symptoms before the onset, sudden loss of consciousness, and death within 1 hour after the appearance of acute symptoms, which is a non-traumatic natural death. The most common sudden death in the clinic is sudden cardiac death, which refers to sudden death due to cardiac causes. After the occurrence of sudden death, basic life support should be started immediately, which is the implementation of hands-on cardiopulmonary resuscitation, calling the emergency system, and defibrillation with an automated external defibrillator as soon as possible. In China, automatic external defibrillators are currently used mainly in public places in large cities, and are not common in small and medium-sized cities, making CPR and calling the EMS system particularly important. Cardiopulmonary resuscitation, mainly chest compressions and mouth-to-mouth artificial respiration. In CPR, firstly, under the premise of ensuring the safety of the environment, place the patient face up on a hard surface, unbutton the coat, take the middle of the sternum as the compression point, fold the hands and press down vertically, the compression depth is required to be at least 5cm, and the compression frequency is 100-120 times/min. Next, press the arms vertically with the sternum for 30 times, then perform mouth-to-mouth artificial respiration for 2 times, and after 5 cycles, call the patient or check the pulse to assess the vital status. If there is no improvement, CPR is continued. If the patient is awake and spontaneous breathing and heartbeat are restored, the next step of treatment is awaited. Current research suggests that cerebral blood flow is interrupted after cardiac arrest and loss of consciousness occurs after about 10 seconds, which may survive with timely resuscitation, otherwise biological death may occur and is difficult to reverse. Therefore, once sudden death occurs, it is important to resuscitate and call 120 emergency as soon as possible.