The invention provides application of general inula helenium sesquiterpene lactone in preparation of a medicine for treating rheumatoid arthritis. The general inula helenium sesquiterpene lactone contains alantolactone and isoalantolactone; and the sum of the contents of the alantolactone and the isoalantolactone accounts for 60 to 90%. The results of animal pharmacodynamic tests show that the general inula helenium sesquiterpene lactone, the alantolactone and the isoalantolactone all can inhibit the clinical onset of CIA (Collagen-induced Arthritis), obviously inhibit the morbidity of CIA, obviously reduce the level of IFN(Interferon)-gamma, and remarkably inhibit the generation of IL(Interleukin)-17. Therefore, the general inula helenium sesquiterpene lactone, the alantolactone and the isoalantolactone all can be used for preparing the medicine for treating rheumatoid arthritis. The medicine is composed of the general inula helenium sesquiterpene lactone serving as an active ingredient and a pharmaceutic adjuvant and can be in form of a troche, a capsule, a soft capsule, a dropping pill, granules, an injection, a powder-injection or an aerosol and the like. The medicine provided by the invention is a new medicine for treating rheumatoid arthritis, which has remarkable curative effect and little side reaction; the raw materials are conveniently obtained, the preparation method is simple, and the medicine has relatively high clinical application value.