Inferior cerebellar tonsillar herniation malformation (Chiari malformation) is the most common craniocervical junction malformation. It usually presents with numbness and sensory hypersensitivity in the occipital, cervical and bilateral upper extremities, dissociative sensory deficits in the upper extremities and progressive muscle weakness and muscle atrophy in the extremities. To clarify the diagnosis, MRI scans of the craniocervical junction area are performed to determine whether there is a submicrocephalic tonsillar herniation deformity and whether it is combined with spinal cord cavitation. For those who have symptoms of neurological compression, surgical treatment is preferred. Depending on the situation, bone window decompression, dural expansion repair, removal of degenerative subhypophyseal herniation of the tonsils and occipitocervical internal fixation and bone graft fusion can be chosen. The aim of surgery is to relieve the compression, promote the recovery of the involved nerve and prevent its further deterioration. This is a recent case of subungual herniation of cerebellar tonsils combined with spinal cord cavity treated by us.