The invention discloses an orally-taking medicine for treating acute gastroenteritis of horses. The orally-taking medicine comprises the following Chinese medicine raw materials by weight percent: 30 of coptis, 30 of Chinese pulsatilla, 50 of andrographis paniculata, 50 of acalypha australis, 50 of purslane, 50 of phoenix-tail fern, 50 of wood avens, 80 of unripe hawthorn, 30 of costustoot, 20 of magnolia officinalis, 30 of pseudo-ginsheng, 20 of brucea javanica and 20 of glycyrrhiza. The preparation method comprises the steps as follows: uniformly mixing the 30 of coptis, the 30 of Chinese pulsatilla, the 50 of andrographis paniculata, the 50 of acalypha australis, the 50 of purslane, 50 of phoenix-tail fern, the 50 of wood avens,the 80 of unripe hawthorn, the 30 of costustoot, the 20 of magnolia officinalis, the 30 of pseudo-ginsheng, the 20 of brucea javanica and the 20 of glycyrrhiza, smashing the mixture, screening the smashed mixture with a sieve of 300 meshes, and storing the medicinal powder in a bottle for standby. The orally-taking medicine provided by the invention has the advantages that the medicinal herb resource of the orally-taking medicine can be obtained easily, the cost is low, the curing speed is high, the effect is obvious, the curing rate is high, the effective rate of treating acute gastroenteritis of horses is 100%, and the curing rate is 100%.