Diagnostic steps of acute syncope: Syncope is a sudden and brief state of loss of consciousness caused by various reasons, accompanied by sudden loss of muscle tone and fall to the ground, loss of consciousness rarely exceeds 20-30 s. Some syncope episodes are preceded by prodromal symptoms such as dizziness, tinnitus, sweating, blurred vision, pallor, and general discomfort, and this period is called the prodromal period. After the attack, symptoms such as fatigue and weakness, nausea, vomiting, drowsiness and even urinary and fecal incontinence occur, which is called the recovery period. Therefore, the whole process of syncope may last for several minutes or longer. Clinically, syncope accounts for about 3% of emergency patients, and effective and rapid initial diagnosis of syncope has a great impact on the patient’s healing and regression. In patients with syncope, because the onset of the disease is often not visible, questioning, physical examination, and relevant ancillary tests are very important to help diagnose or evaluate the disease. In emergency medicine, the following syncope diagnostic procedures can be referred to: (1) careful history taking, systematic physical examination, laboratory tests, electrocardiography, cranial CT, MRI; (2) definite or suggestive diagnosis can be made for some patients according to the examination results; (3) if the diagnosis is not clear, organic cardiac pathology should be excluded first; (4) if there is no organic cardiac pathology, if the attacks are severe and frequent Consider neuroreflex syncope and give tilt test or carotid massage test to confirm the diagnosis. For the first attack or few attacks with unknown cause, observation and follow-up can be given. History and symptoms of syncope caused by fear, severe pain, emotional stimulation, standing for too long, etc. are diagnosed as vasovagal syncope; syncope in special cases, such as coughing, sneezing, gastrointestinal stimulation (swallowing, visceral pain, stool), urination (before urination) and excessive exercise are considered situational syncope; those with symptoms such as syncope and palpitations before the attack are highly suspected of cardiogenic syncope; metabolic diseases Patients may have metabolic syncope; those with symptomatic syncope accompanied by postural hypotension are definitively diagnosed as postural syncope. Cerebrovascular syncope should be considered if there is blood loss, first blood volume, diarrhea, syncope with neurological signs such as vertigo, headache, and numbness of the limbs. Laboratory tests Patients with severe anemia are considered for syncope due to blood loss. Blood biochemical tests suggesting hypoglycemia can be considered as syncope caused by hypoglycemia. ECG, CT examination Patients with palpitations and palpitations as well as ECG examination suggestive of arrhythmia should be considered or diagnosed as arrhythmogenic syncope; syncope with evidence of acute myocardial ischemia (chest pain, ECG manifestations) is diagnosed as myocardial ischemic syncope even without myocardial infarction. Cranial CT, MRI exclude or may clarify neurological syncope. Syncope of unknown origin should be considered when the diagnosis is still not clear based on the patient’s history, signs and relevant ancillary examinations. For syncope of unknown cause, the following aspects should be examined: 1. cardiovascular organic disease, cardiac echocardiography, stress test, ambulatory ECG and electrophysiological examination; 2. neuroreflex syncope, syncope with normal ECG and no organic heart disease, especially in patients with recurrent or severe syncopal episodes, the possibility of neuroreflex syncope should be considered first. Tilt test or carotid massage test can be given; 3. Patients with recurrent syncope and with multiple psychiatric symptoms such as tension and anxiety should be evaluated for neurological aspects. The special nature of the emergency environment and the critical nature of emergency diseases determine that the emergency medical personnel need to make a diagnosis of patients with emergency syncope as soon as possible under the guidance of a rapid, comprehensive and orderly thinking in the diagnosis and treatment of syncope. Those with a clear diagnosis can be given the appropriate treatment or admitted to hospital.