The invention discloses an external preparation for treating leucoderma and a preparing method. The external preparation mainly comprises, by mass, 8 parts to 15 parts of cortex dictamni, 7 parts to 12 parts of pericarpium juglans, 9 parts to 13 parts of dry lotus flowers, 6 parts to 12 parts of small goosefoots, 8 parts to 16 parts of jasminum elongatum, 7 parts to 14 parts of maesa japonica, 9 parts to 15 parts of notopterygium roots, 6 parts to 10 parts of white muscardin silkworms, 8 parts to 13 parts of roots of gourian clematis, 10 parts to 14 parts of pararuellia delavayana, 7 parts to 13 parts of lithargyrum, 9 parts to 14 parts of tribulus terrestris flowers and 8 parts to 12 parts of porana flowers. The external preparation is made of traditional Chinese medicine materials, is locally used and is safe, reliable and wide in suitable crowd. The compound has the effects of clearing damp, detoxifying, dispelling the wind, activating blood and the like, is good in curative effect, capable of preventing relapsing and free of obvious toxic and side effects.