The invention relates to biological fermentation day cream and a preparation method thereof. The preparation method comprises the following steps: firstly, feeding cetearyl alcohol, natural jojoba oil, squalane, superfine titanium dioxide and vitamin E into an oil phase pot, heating to 75-80 DEG C, sufficiently stirring and uniformly dissolving; pouring all water into a water phase pot, subsequently slowly pouring glycerin and oligomerization maltose glucoside, adding hyaluronic acid, holding the temperature for half an hour after the raw materials are all dissolved; performing suction filtration on the oil phase in the oil phase pot into an emulsification pot, stirring, slowly homogenizing, and performing suction filtration on the water phase in the water phase pot into the emulsification pot; after completely sucking the material, rapidly homogenizing for 3 minutes, stopping homogenization, sequentially adding essences, an aloe extract and a composite fermented amino acid total effective nutrient liquid, uniformly stirring, completely adding the materials, continuously stirring for 30 minutes, cooling down and vacuuming through the whole process. Compared with the prior art, the day cream is gentle in property, has the functions of remedying, moisturizing and tightening skin and resisting wrinkles, at the same can prevent environment damage (such as ultraviolet ray and air pollution) to the skin, and can effectively prevent the skin from external pollution which can cause early aging of the skin.