The invention discloses a plaster for treating ankylosing spondylitis and a preparation method thereof. The plaster disclosed by the invention contains more than forty kinds of traditional Chinese medicine ingredients, such as angelica, radix paeoniae alba, radix achyranthis bidentatae, rhizoma drynariae, salted rhizoma cibotii, eucommia bark, curculigo rhizome, fleece-flower root, morinda root, ligustrum lucidum, prepared rehmannia root, epimedium and deer-horn glue. The plaster disclosed by the invention is convenient to prepare, convenient to use, safe in clinical application, high in effective ingredient absorption, good in medicine property exertion and remarkable in treatment effect, directly reaches the affected site during external application, treats both symptoms and root causes and does not stimulate the internal organs. Through combining all the ingredients, the treatment effect is improved, the medicine property is changed or mitigated, and the toxicity and side effects of the drug are reduced or eliminated; the traditional Chinese medicine plaster disclosed by the invention is specially used for treating ankylosing spondylitis and has a relatively good symptom treatment or alleviation effect on the treatment of ankylosing spondylitis, and during the treatment of 71 patients in all, the total effective rate reaches 96%. In addition, the plaster disclosed by the invention contains camphor, plum borneol and the like, so that the corticosteroid transdermal capability can be increased by 8-10 times.