Headache is one of the most common clinical symptoms involving various departments, especially in neurological diseases, and its etiology is very complex. The incidence is high, with almost 90% of the population having a headache attack in their lifetime. In fact, headache is a symptom, not a disease, and is an external manifestation of the body induced by a certain disease. When a headache occurs, it is first determined whether it is an intracranial or extracranial disease. If it is determined to be an intracranial disease, it is necessary to determine which specific disease it is. If it is difficult to determine, more serious diseases should be excluded first: cerebral hemorrhage, subarachnoid hemorrhage, massive cerebral infarction, encephalitis, meningitis (the above diseases can be confirmed by cranial CT or MRI). Then, consider whether it is caused by the following common diseases: migraine, tension headache, cluster headache, neuropathic headache, upper respiratory tract infection, etc. For extracranial diseases, it is important to consider whether it is a poisoning or a systemic infection. If it is poisoning, it is necessary to diagnose what kind of poisoning; if it is systemic infection, it is necessary to diagnose what part of the body is infected. Therefore, if a headache occurs, it is recommended to have a clear examination before further treatment, so as not to worry about the condition.