The invention discloses a preparing method of a pharmaceutical composition for treating emesis, and relates to the technical field of traditional Chinese medicine composition preparation. The composition comprises, by weight, 15-900 parts of coptis chinensis and 100-800 parts of folia perillae acutae. The preparing method includes the steps that by weight, 1/4-3/4 of coptis chinensis is weighed and smashed for use; 40-80% ethyl alcohol is used for extracting the remaining coptis chinensis in a reflux mode, and ethyl alcohol is recovered from an extracting solution until the extracting solution is free of alcohol taste for use; volatile oil is extracted from folia perillae acutae through a steam distillation method, the volatile oil and a water solution obtained after volatile oil extraction are collected for use, water is added to decoction dregs, the mixture is boiled, extracted and filtered, obtained filter liquor, the water solution obtained after volatile oil extraction and the coptis chinensis extracting solution are converged, and the mixed solution is concentrated into clear paste with the relative density being 1.00-1.30 (60-80 DEG C); the clear paste, the coptis chinensis powder and starch are pelletized and dried, the volatile oil is sprayed, and the product is put into capsules to prepare a capsule agent. The composition is free of side effects and treats both symptoms and root causes, and the medicine prepared through the preparing method has a better pharmaceutical effect.