The invention discloses a preparation method of 3-(difluoromethyl)-1-methyl-1H-pyrazol-4-carboxylic acid. The reaction formula is shown in the specification. Difluoroacetic acid, which is relatively low in price and small in molar mass and is introduced at a post-synthesis phase is adopted, so that the preparation method of the 3-(difluoromethyl)-1-methyl-1H-pyrazol-4-carboxylic acid is low in cost, simple and safe in technological operation, high in product content, and high in product yield; the content is 98.1-98.9% (liquid chromatogram, external standard); the total yield is 52.2-56.9% (based on propargyl alcohol). Nanoscale titanium dioxide is adopted to carry out catalytic esterification, so that the reaction yield is high; the reaction time is short; the used raw materials and solvent are cheap and available; furthermore, an organic solvent is avoided in the four reaction steps, so that the solvent recovery cost and the environmental pollution risk are greatly reduced.