Preparation and application of line leaf inula flower lactone A in the multiple sclerosis, having a structure of Line leaf inula flower lactone A has therapeutic effects on experimental autoimmune encephalomyelitis (EAE) model, and is used to develop drug for treating multiple sclerosis (MS). Line leaf inula flower lactone A drug is a combination containing the active ingredient of line leaf inula flower lactone A and conventional pharmaceutically carrier, and may be in forms of tablets, dispersible tablets, mouth collapse tablets, retard tablets, capsule, soft capsule, dropping pill, granules, injection, powder injection, or aerosol. The pharmaceutical composition is used for treating multiple sclerosis, has tremendous developing potentiality because of its high value of clinical application.