The invention discloses a medicine for relieving a cough and a preparation method thereof. The medicine for relieving the cough comprises the following raw materials in parts by weight: 15 to 25 partsof barberry root, 4 to 6 parts of inula flower, 4 to 6 parts of rhizoma bolbostemmae, 2 to 4 parts of dried tangerine or orange peel, 4 to 6 parts of radix bupleuri and 2 to 4 parts of Pinellia ternate. The preparation method comprises the following steps: adding the raw materials into water with the amount of 6 to 8 times of total weight of the medicinal materials, decocting the mixture with slow fire for 25 to 35 minutes after boiling with strong fire, and taking a filter liquor; then adding water with the amount of 6 to 8 times of total weight of the medicinal materials into dregs of a decoction, decocting the mixture for 25 to 35 minutes after boiling with strong fire, and after merging the filter liquors twice, uniformly mixing the filter liquors to obtain the medicine. The medicinehas the characteristics of taking effect quickly, good in curative effect, safe and free of toxic and side effects. The medicine is used for 60 patients clinically, and the total effective rate is 90%.