The invention relates to the technical field of cosmetics, and discloses a double hyaluronic acid stock solution and a preparation method thereof. The double hyaluronic acid stock solution is preparedfrom the following raw material components in percentage by weight: 0.05%-0.5% of hyaluronic acid A, 0.05%-5% of hyaluronic acid B, 0.01%-1% of transparent Xanthan gum, 3%-9% of glycerin, 2%-6% of butanediol, 0.5%-5% of oat kernel extract, 0.5%-5% of oat beta-glucan, 0.5%-5% of moisturizing factors, 1%-5% of aloe barbadensis leaf juice, 0.1%-0.5% of a polyacrylate cross-linked polymer-6, 0.005%-0.008% of essence, 0.02%-0.04% of a solubilizer, 0.4%-0.6% of a preservative and the balance of deionized water. According to the double hyaluronic acid stock solution and the preparation method thereof, the ratio of two kinds of different molecular weight hyaluronic acid are reasonably adjusted in a ground-breaking mode to form a thin film on the surface of skin, so that moisture in the skin is effectively locked, the effect of long-term moisturizing is achieved, and meanwhile, the skin is smooth but not greasy, no matter in a cold winter or a hot summer, the use experience is good, the cost is lower, and the double hyaluronic acid stock solution is easy to accept by the public.