Aquaporin-4 was a highly preferential water channel protein,participating in the reabsorption of the cerebrospinal fluid and the osmoregulation.Investigation showed aquaporin-4 played an important role in humoral-mediated immunologic mechanism of neuromyelitis optica (NMO).Meanwhile,NMO revealed an autoimmune channel disease,and the study on the immunopathogenesis of NMO was ushered into a new stage. AQP4 would be a new research field for the diagnosis and therapy of NMO.