Optic neuromyelitis optica and multiple sclerosis are two different diseases. In the past, optic neuromyelitis optica was considered a subtype of multiple sclerosis, and the two diseases were often not differentiated in terms of diagnosis and treatment. This is inappropriate. Currently, it turns out that more and more evidence suggests that optic neuromyelitis optica and multiple sclerosis are two different diseases. Optic neuromyelitis optica is more prevalent in Asia, Latin America and other regions. Our country also belongs to the high incidence area. Middle-aged and older women are the susceptible population. Optic neuromyelitis optica is relatively uncommon in the Caucasian populations of Europe and the United States. Optic nerve damage in optic neuromyelitis optica tends to be more severe, with more cases of simultaneous or repeated damage bilaterally. Spinal cord lesions tend to be long segmental (>3 vertebral segments) and can have significant swelling. Optic neuromyelitis optica can present with intracranial lesions that are characteristically located in midline structures such as the thalamus, corpus callosum, and dorsal aspect of the brainstem. Optic neuromyelitis optica is more hormone-dependent in treatment, requiring high dose shocks of hormones in the acute phase, after which oral hormones need to be tapered slowly, especially to 6 tablets after which they need to be tapered more slowly. Immunosuppressants such as azathioprine and CTX can be used in remission to reduce recurrence. Interferon is not recommended for the prevention of recurrence of optic neuromyelitis optica. Antibodies to aquaporin 4 are specific for optic neuromyelitis optica, while antibodies to aquaporin 4 in multiple sclerosis are negative. The combination of optic neuromyelitis optica with other systemic autoimmune diseases, such as dry syndrome and SLE, is more common, but this is not common in multiple sclerosis. Multiple sclerosis predominates in Caucasians. The number of patients with multiple sclerosis in China has also increased in recent years. Optic nerve damage in multiple sclerosis is mostly unilateral and less severe than in multiple sclerosis. The spinal cord lesions are short-segmented, and intracranial lesions are mostly located around the lateral ventricles, subcortical, and the cerebellar brainstem are also involved. The acute phase of treatment is characterized by high-dose hormone shocks, with faster reduction than in optic neuromyelitis optica, and mostly without long-term oral hormone administration. In the remission phase, interferon can be injected subcutaneously.