The invention provides a preparation method of sucrose fatty acid ester. The preparation method comprises the following steps: A) performing a reflux reaction of sucrose and alkyl ester in the presence of an alkali catalyst in a solvent mixture to produce a product mixture; B) adding a saturated sodium chloride solution to the product mixture, adjusting pH to 6.6-7.2, adding an alcohols extractant for extraction, and performing liquid separation to obtain an organic phase; and C) performing reduced-pressure concentration and evaporation to dryness to obtain sucrose fatty acid ester. The invention belongs to the technical field of industrial chemistry and provides the preparation method which is simple in steps and mild in reaction condition. High-purity low-substitution-degree sucrose fatty acid ester is prepared through the method and is good in performance. The environmental benefit is good.