The invention relates to a preparation method of gallic acid alcohol ester with a molecular formula (HO)3C6H2COOCnH2n+2 (n=6, 8, 12 or 16). In the method of the invention, aminosulfonic acid is used as catalyst in solvent benzene or toluene and the molar ratio of gallic acid to primary alcohol and aminosulfonic acid is 1.0:1.1-1.5:0.08-0.20. The method comprises the following steps: reacting gallicacid with primary alcohol for 6-10h at 90-130 DEG C, adding recrystallization solvent in the mixture, stirring to resolve the mixture completely, performing heat filtration, cooling the filtrate to precipitate crystal, centrifuging or filtrating to obtain a raw product, decoloring and drying to obtain the finished product. The yield of the finished product can reach above 90%, the catalyst cost can be reduced by about 70-90%, the product has stable quality, low cost and high yield so that the method of the invention is applicable to mass industrialized production.