Abstract:Non-syndromic microtia is mainly manifested as external and middle ear deformity, usually not associated with other parts of the deformity, most cases are sporadic.Some scholars believe that non-syndromic microtia is the second largest craniofacial congenital deformity in China.It may be one of the milder clinical manifestations of hemifacial microsomia.Hemifacial microsomia was caused by hypoplasia of the first and second branchial arches.Although there has been a lot of literature on non-syndromic microtia with familial aggregation and partial genetic variation.However, this does not explain most of the phenotypes of non-syndromic microtia, which is still developed by individuals with genetic predisposition in specific environments.It has been reported that retinoic acid, thalidomide, mycopherlate and immunosuppressive drugs can cause microtia without syndrome. The mechanism may be related to the disturbance of neural crest cell migration and local vascular rupture.Therefore, we will introduce the neural crest cell hypothesis and vascular rupture hypothesis to explain the non-syndromic microtia.