Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is a type of newly recognized autoimmune encephalitis which is commonly seen in children, but its precise etiology is still uncertain. To reveal the etiology of anti-NMDAR encephalitis is very necessary for understanding its pathology, and for starting immune-related therapy as early as possible to improve its prognosis. In the initial literature, tumor, especially teratoma is more related with the anti-NMDAR encephalitis. In recent research, its etiology is related to infection and heredity. This article reviews the recognition and variation of the etiology of anti-NMDAR encephalitis.