A preparation method and use of a difluoroallyl boronic ester are disclosed, which belongs to the field of compound preparation. In the preparation method of the difluoroallyl boronic ester, a reaction is carried out by using a compound represented by formula (II) and bis(pinacolato)diboron as raw materials in a solvent, in the presence of an iron catalyst and a base, according to the following reaction scheme, to obtain the compound represented by formula (I). The method directly uses an inexpensive, commercially available metal iron salt as a catalyst to provide a convenient, low cost method for the preparation of the difluoroallyl boronic ester and provide an effective approach for the synthesis of γ-aminobutyric acid receptor agonist (III).