The invention relates to a novel preparation method of a darifenacin intermediate 2,3-dihydro-5-benzofuran acetic acid. The preparation method comprises the following steps: by taking acetal of hydroxyphenylacetic acid and bromoacetaldehyde as an initial raw material, carrying out an O-alkylation reaction in the presence of alkali so as to obtain a corresponding ether compound; carrying out an esterification reaction to obtain a corresponding ester; performing cyclization to obtain 2,3-benzofuran-5-acetate in the presence of PPA (Polyphosphoric Acid); hydrolyzing and acidizing the 2,3-benzofuran-5-acetate to obtain a corresponding carboxylic acid; performing catalytic hydrogenation to obtain 2,3-dihydro-5-benzofuran acetic acid; or performing catalytic hydrogenation on the 2,3-benzofuran-5-acetate so as to obtain 2,3-dihydro-5-benzofuran acetate; and hydrolyzing and acidizing, thereby obtaining the 2,3-dihydro-5-benzofuran acetic acid. The method disclosed by the invention is simple and safe, cheap and readily available in reactive raw materials and high in reaction yield and is particularly applicable to industrialized production of the 2,3-dihydro-5-benzofuran acetic acid.