The invention relates to an oral traditional Chinese medicine for treating skin diseases. The oral traditional Chinese medicine is prepared from radix lithospermi, rhizoma smilacis glabrae, fructus gardeniae, cortex dictamni, common peony roots, radix scrophulariae, rehmanniae radix, isatis indigotica forts, radix sophorae flavescentis, lalang grass rhizome, flos sophorae, radix sileris, puncturevine caltrop fruits, red-rooted salvia roots, ligusticum wallichii, large-leaved gentian, processed polygonum multiflorum, Chinese angelica, white paeony roots and licorice roots. The oral traditional Chinese medicine is a pure traditional Chinese medicine prescription, reduces the recurrence rate of psoriasis and obviously improves the cure rate. In the invention, by mixing the Chinese angelica, the white paeony roots, the isatis indigotica forts and the licorice roots for use, the organism immunity can be enhanced greatly and the problem of recurrence of the psoriasis due to cold and pharyngitis can be solved. The oral traditional Chinese medicine has high effective rate to the psoriasis more than 98 percent and also has 100 percent cure rate to conventional skin diseases such as acne, cutaneous pruritus, pityriasis rosea, eczema, lichen planus, neurodermatitis, urticaria, seborrheic dermatitis, and the like.