After the onset of facial palsy, most patients begin to recover gradually after one week, and most recover completely within two months, but some patients do not recover completely. The most common cause of sudden unilateral facial palsy is stroke and idiopathic facial nerve palsy, and it is usually determined first whether it is due to a central or peripheral nervous system disorder. Facial palsy is often preceded by peri-auricular pain, and weakness usually occurs suddenly but may progress over a few hours to about a day, and may cause taste disturbances, tearing, or auditory hypersensitivity. Bilateral facial palsy is rare; if present, consider the possibility of acute inflammatory demyelinating polyneuropathy, and if cerebrospinal fluid cell counts are increased, Lyme disease is likely. The diagnosis of facial palsy is not difficult, and attention should be paid to identifying the cause of facial palsy, such as acute idiopathic facial nerve palsy, acute stroke, acute inflammatory demyelinating polyneuropathy, otogenic, and posterior cranial fossa lesions, etc. Timely and effective treatment for the cause can yield significant results.