The invention relates to a preparation method of a veterinary injection having the functions of clearing heat-toxin and removing heat from the blood and relieving diarrhea, which comprises the steps: (1) after going through impurity removal, yellowish sophora root and whole windflower go through pretreatment for standby; (2) extraction is carried out to crude drugs of yellowish sophora and the windflower, water with a quantity 8 times of the crude drugs is used for carrying out vacuum dynamic extraction and concentration at the low temperature not more than 70 DEG C and until the colors of the crude drugs become light; and (3) the concentration solution is added with 0.5 percent (weight percentage) of activated carbon, boiled for 10min, added with 10 percent to 60 percent (weight percentage) of hydrophilic macromolecular substance as an additive, added with 0.1 percent to 3 percent (weight percentage) of tween-80 and water for injection for constant volume until each 1000ml of solution contains 0.5kg to 2.5kg of yellowish sophora crude drugs and 0.5kg to 2.5kg of windflower crude drugs. The veterinaryl drug is pure Chinese medicine preparation, has remarkable curative effect, low costs and no drug residue and can achieve the effect of permanent cure.