·AIM:To devote much attention to the study on diagnosis and treatment of optic neuritis(ON)and multiple sclerosis(MS).·METHODS:The 21 ON among the patients of MS who were admitted to eye center of the affiliated hospital of Mudanjiang medical university from 2004 to 2008 were retrospectively analyzed,clinical symptom,diagnosis and therapy of MS with first-diagnosis of ON were investigated.·RESULTS:According to Poser and MRI criteria of diagnosis,21 cases were identified as MS.Through treatment of a large dose of methylprednisolone,the visual acuity of 15 cases(71%)was improved.·CONCLUSION:It is necessary for patients with optic neuritis to do conventional MRI to exclude MS.A large dose of methylprednisolone is the first choice.·