The invention belongs to the technical field of oral emulsion preparations, and particularly relates to long-acting composite vitamin oral emulsion for livestock and a preparation method thereof. The emulsion comprises vitamin A, vitamin D, vitamin E, vitamin B, vitamin B2, vitamin B6, vitamin C, non-ionic surface active agents A, non-ionic surface active agents B, soybean lecithin, a solvent, an antioxidant, EDTA-2Na and the balance water for injection. According to the long-acting composite vitamin oral emulsion for the livestock and the preparation method thereof, the particle size of the prepared emulsion ranges from 0.1 micron to 50 microns, the prepared emulsion is prone to being absorbed after the emulsion enters livestock bodies, the acting time is long, clinical administration is convenient, the emulsion is suitable for community administration, and the manpower and the material resources are saved.