Homer syndrome results from an interruption of the oculosympathetic pathway.Typical clinical manifestations include ptosis,dilated pupils and less sweat on the affected side.The clinical symptoms caused by damage at different sites are not identical.An in-depth understanding of Horner syndrome may help us identify the causes of Horner syndrome early and estimate the severity of the disease.This article reviews the neuroanatomy and common etiology,clinical manifestations,diagnosis and treatment of Horner syndrome to provide reference for clinical work.