The invention provides a process for preparing an ascorbic acid ester. Ascorbic acid and fatty acid are used as raw materials. The process comprises the following steps of: cooling the reacted mixture after sulfuric acid catalytic synthesis, adding water into the mixture, extracting the mixture by using mixed solution of aliphatic monoaldehyde and halogenated hydrocarbon, washing the extract by using water, evaporating the extract to obtain a coarse product, re-crystallizing the coarse product by using the halogenated hydrocarbon, and filtering, washing and drying the re-crystallized product to obtain high-purity ascorbic acid-6-fatty acid ester. The process is operated in the same reaction kettle, and the extracting process is in a liquid-liquid form so as to avoid the defects of difficult filtering and drying and difficult moisture removal in the prior art; the extracting solution well dissolves the esterification product and is easily separated from the water, the byproduct is little, and particularly the disadvantages that the purity of a target product is reduced and the quality becomes poor due to emulsification during acid washing in the prior art are avoided; and the coarse product is re-crystallized by using the halogenated hydrocarbon so as to effectively remove a little amount of residual fatty acid which is not totally extracted. The yield of the fatty acid ester product of the ascorbic acid ester produced by the process is over 70 percent, and the purity is over 98 percent.