The invention discloses a small-molecule hyaluronic acid and a preparation method thereof, wherein the small-molecule hyaluronic acid comprises the following components in mass percent: 0.1-5% glycerin, 0.1-10% propylene glycol, 0.1-10% butanediol, 0.1% ~1% fruit peel extract, 0.1~1% hydrolyzed sodium hyaluronate, 0.1~5% glycerol glucoside, 0.1~5% glucosaminoglycan, 0.1~10% hydrolyzed collagen, 0.1~1% carbomer , 0.1-1% triethanolamine, 0.1-2% bis(hydroxymethyl) imidazolidinyl urea, 0.1-1% iodopropynyl butyl carbamate, and the balance is deionized water. The present invention also provides a preparation method of small molecule hyaluronic acid, comprising 1) preparing citrus peel extract for standby use, 2) batching, 3) raising the temperature to prepare stock solution, 4) preparing crude product, and 5) improving quality. The hyaluronic acid prepared by the invention has a molecular weight of 500,000 to 800,000 daltons, which is beneficial to the skin's absorption, and simultaneously adopts fruit peel extracts and easy-absorbed organic matter, which is beneficial to the health of the skin.