The invention provides psoriasis treatment medicine and a preparation method and a detection method. The psoriasis treatment medicine is mainly composed of radix rehmanniae, saponin, oldenlandia diffusa, cortex dictamni, lithospermum, rhizoma smilacis glabrae, isatis root, paeonia suffruticosa, sophora flower, rhizoma anemarrhenae, red peony root, gypsum, bistort rhizome, burdock, cicada slough, indigo naturalis, honeysuckle, salviae miltiorrhizae, licorice and arisaema cum bile. The preparation method comprises the following steps: mixing radix rehmanniae, saponin, oldenlandia diffusa, cortex dictamni, lithospermum, rhizoma smilacis glabrae and isatis root, adding water for decocting twice, filtering to obtain filtrate, crushing the reset components to fine powder, sieving, uniformly mixing, and adding the mixed powder into the filtrate to process pills via water. Thin layer chromatography is used for detecting. The psoriasis treatment medicine provided by the invention abides by the principle of formulating prescription in traditional Chinese medicine of assistant and guide, the herbs are combined to ensure the functions of warm reinforcing liver and spleen, dispelling wind and eliminating dampness, regulating qi and blood, clearing and activating the channels and collaterals, promoting blood circulation to remove blood stasis, strengthening the body resistance to eliminate pathogenic factors, adjusting the immunity, and perfecting skin microcirculation, the psoriasis treatment medicine is used for preventing and treating psoriasis, is exact in curative effect and free of toxic side effects, and a variety of traditional Chinese medicine preparations are convenient to take.