The invention discloses a preparation method of 2,5-dimethyl-4-hydroxyl-3(2H)furanone. The preparation method comprises following three steps: (1) taking an easily available 3,4-diacetyl-2,5-hexanedione as the primary raw material, and carrying out intra-molecular dehydration to close the ring to obtain 2,5-dimethyl-3,4-diacetyl furan in the presence of a catalyst; (2) oxidizing 2,5-dimethyl-3,4-diacetyl furan through Baeyer-Villiger oxidation to obtain 2,5-dimethyl-3,4-diacetoxyl furan; and (3) hydrolyzing 2,5-dimethyl-3,4-diacetoxyl furan to obtain 2,5-dimethyl-4-hydroxyl-3(2H)furanone. Theused raw material 3,4-diacetyl-2,5-hexanedione is prepared through coupling or electrochemical coupling of acetyl acetone under the action of NBS and an alkali; the raw material preparation is simple, the raw material is easily available, at the same time, the synthesis route is short, the yield is high, the synthesis conditions are mild, the operation is simple, the purification method is simple, the yield is high, no toxic gas such as hydrogen bromide is generated, and the generated wastewater, waste solids, and waste gas are little.