The invention provides an external-use traditional Chinese medicinal tincture for treating psoriasis. The external-use traditional Chinese medicinal tincture is prepared from the following medicinal materials in parts by weight: 0.5-5 parts of fructus psoraleae, 0.5-5 parts of the root bark of shaggy-fruited dittany, 0.1-0.2 part of safflower carthamus, and 0.5-5 parts of radix notoginseng. A preparation method of the external-use traditional Chinese medicinal tincture comprises the following steps: smashing or cutting up the medicinal materials, placing the obtained medicinal materials into a bottle with the suitable size, adding alcohol into the bottle, covering the bottle with a cover for sealing, soaking the obtained medicinal materials for one week, filtering out dregs, and taking the medicinal solution, thus obtaining the traditional Chinese medicinal tincture. The medicinal materials are in dialectic compatibility, supplement each other in the aspect of function, and are directly fed to the focus, thus the efficacies of dispelling pathogenic wind and removing dampness, as well as dissipating blood stasis and dredging collaterals are effectively exerted, and finally, the purpose of treating psoriasis is achieved.