A method for preparing a traditional Chinese medicine for treating anal cryptitis belongs to the technical field of preparation methods of traditional Chinese medicines. The prior anal sinusitis is generally treated by using oral drugs or infusion antibiotics, which easily causes side effects like vomiting, headache, fever, skin rash and the like; the technical proposal of the invention is as follows: taking 25 kinds of the following herbs such as raw Gardenia, sophora flavescens, scutellaria, akebia stem, asiatic plantain seeds (wrapped by cloth), alisma orientale, Chinese honeylocust spine, gentiana macrophylla, Chinese atractylodes, radix sileris, cyrtomium fortunei, saxifrage, Japanese cayratia herb, roots of rubus crataegifolius, indigowoad leaf, radix isatidis, herba patriniae, sargentgloryvine stem, Pariphyllin, Chinese Lobelia Herb, Japanese ampelopsis root, dandelion, phellodendron, raw rhubarb (being soaked later) and raw liquorice; soaking the 25 kinds of herbs into water except the raw rhubarb and asiatic plantain seeds, then decocting the herbs on slow fire; putting the raw rhubarb into the herbs to continue decocting; filtering and deslagging the decocted liquid medicines to obtain the traditional Chinese medicine for treating anal cryptitis; the medicine has the advantages of simple preparation, little side effects, direct effect on anal cryptitis focus and high cure rate.