The invention discloses animal milk with a function of assisting blood fat reduction and a preparation method thereof. The animal milk comprises the following components in percentage by volume: 97.13 to 98.59 percent of raw material milk, 0.3 to 3mg/ml of thickening agent, 0.8 to 1.5mg/ml of emulsifier, 8.5 to 12.5mg/ml of plant stanol ester or 5 to 7.25mg/ml of plant stanols, 2.5 to 7.5mg/ml of fish oil and 2 to 6mg/ml of lecithin. The preparation method comprises the following steps: (1) preheating the animal milk to a temperature of between 75 and 80 DEG C, adding the thickening agent and the emulsifier, and uniformly stirring; (2) adding lecithin, plant stanol ester or plant stanols, and uniformly stirring; (3) adding the fish oil, diluting to a certain volume, and standardizing; and (4) homogenizing, and sterilizing. Currently, a food combined with plant stanol ester or plant stanols, lecithin and fish oil to achieve the function of assisting blood fat reduction does not exist in the market, and the animal milk with the function of assisting blood fat reduction fills up the blank in the market.