Arachnoid cyst is a congenital disease, a cystic occupancy formed by intracranial cerebrospinal fluid encapsulated by the arachnoid membrane, a kind of benign brain cyst, without genetic predisposition, does not invade the brain, mostly single, a few multiple, often located in the brain fissure and brain pool. In large size, it can compress both brain tissue and skull, which can produce neurological symptoms and cranial changes. Arachnoid cysts in children account for 75% of cases, most of which are found incidentally due to trauma or examination and can be asymptomatic. The best diagnostic method is CT or MRI. CT bone window images can reveal cranial changes such as thinning of the skull under pressure. Pediatric arachnoid cysts are divided into two categories: congenital and secondary, with congenital arachnoid cysts caused by abnormal growth and development. Secondary arachnoid cysts are mostly the result of extensive adhesions to the arachnoid membrane due to trauma and inflammation. Congenital arachnoid cysts are pouch-like structures formed when cerebrospinal fluid is enclosed within the arachnoid membrane and does not communicate with the subarachnoid space. Secondary to arachnoid adhesions, cysts are formed in the subarachnoid space containing cerebrospinal fluid. They occur in the posterior cranial recess, but also in the greater occipital pool, the periaqueductal brain pool, and the suprasellar pool. Intracranial arachnoid cysts can be classified into congenital, traumatic, and post-infection arachnoid cysts depending on their etiology. Asymptomatic arachnoid cysts with no pressure on the brain tissue can be treated without surgery or medication, with regular review of the cranial CT. The following types of arachnoid cysts require surgery: (1) brain displacement, elevated cranial pressure, and local cranial thinning; (2) combined epilepsy; (3) symptoms of local nerve compression; (4) combined hemorrhage; (5) progressive cyst enlargement; (6) giant arachnoid cysts in children, usually >6 cm, require surgery. Those with symptoms should be operated to remove the cystic fluid and excise the surface part of the cystic wall, and cut the inner wall to connect with the subarachnoid space. Good results can often be obtained. For those with hydrocephalus, if the symptoms of increased intracranial pressure are not relieved by the above surgery, or if the cyst recurs after surgery, cerebrospinal fluid shunt is feasible. If ectopic choroid plexus is found in the cyst during surgery, it should be removed by electrocoagulation. The treatment of this disease is to remove the cyst, repair the dural defect and repair the skull defect.