The invention relates to a preparation method of a
telmisartan intermediate, namely 2-n-propyl-4-methyl-6-Benzimidazolecarboxylic acid. The preparation method of the 2-n-propyl-4-methyl-6-Benzimidazolecarboxylic acid comprises the following steps: firstly,
ethanol hydrochloride acts with
butyronitrile and
anhydrous hydrogen chloride within the range of 0-35 DEG C; the mixture obtained in the firststep reacts with 3-methyl-4-
aminobenzoic acid and ice vinegar within the range of pH 5.0-11.0 at the controlled temperature of 10-40 DEG C, and an intermediate shown in the formula II is obtained; and then the intermediate shown in the formula II reacts with a
sodium hypochlorite solution, and the 2-n-propyl-4-methyl-6-Benzimidazolecarboxylic acid is obtained. The intermediate preparation processis suitable for industrial production, and meanwhile the product quality is improved.