The present invention discloses a 5-benzyloxy-4-oxo-4H-pyran-2-carboxylic acid preparation method comprising the following steps: adding kojic acid, benzyl chloride and methanol benzyl chloride into a reaction vessel, and heating for reflux reaction for 16 to 18 hours; distilling under reduced pressure, evaporating the solvent to dryness, and cooling to room temperature; adding methanol and water, stirring, washing, filtering and drying to obtain an intermediate; and adding the intermediate and water into the reaction vessel, reducing the temperature to 0 DEG C to -10 DEG C, adding sodium periodate, controlling the temperature to be not higher than 5 DEG C, then adding dropwise a proper amount of water, stirring for 5-15 minutes, heating to 12 DEG C-22 DEG C, stirring for reaction for 2.5 to 3.5 hours, extracting with ethyl acetate, layering, drying, filtering and drying to obtain white solid 5-benzyloxy-4-oxo-4H-pyran-2-carboxylic acid. The new 5-benzyloxy-4-oxo-4H-pyran-2-carboxylic acid preparation method is provided, does not produce large amounts of chromium-containing waste water, prevents severe environmental pollution, and can achieve industrial production.