The invention relates to compound vitamin nanoemulsion, belonging to the pharmaceutical technical field. the preparation method of the nanoemulsion per 1000ml comprises the following steps: fully mixing 150-240g of AEO-9 or AEO-4, 200-350g of Tween-80, 80-120g of benzyl alcohol and fat-soluble active ingredients at 30-60 DEG C to obtain oil phase, then adding water to dilute, and performing constant volume process, wherein the fat-soluble active ingredients comprises 60-180 million IU of vitamin A, 18-48 million IU of vitamin D and 25-75g of vitamin E, and vitamin K3 and dihydropyridine can be further added in the product. The product is clear and transparent, the average grain diameter is less than 10nm, the product has good dispersion stability; after nanoparticlization, vitamin A, D, Eand K has high efficiency and long-term effect and can be directly absorbed and used by the small intestine without bile, the absorptivity is 100%, and the bioavailability is about 98%. The product can be used in the livestock production; and even if the livestock and poultry have hepatic diseases or fat-absorbing disorders, the absorption of fat-soluble vitamins can not be affected, thus playinga very positive significance in improving the physique of livestock and poultry with diseases and shortening the treatment period.