This invention belongs to the field of grape cultivation technology, specifically relating to a fruit enlargement agent for Daqing grapes, its preparation method, and its application. The fruit enlargement agent for Daqing grapes is prepared from an
aqueous solution of
gibberellin, thiabendazole, and
brassinolide. Specifically, the concentration of
gibberellin in the fruit enlargement agent is 20 mg / L~25 mg / L, the concentration of thiabendazole is 1.0 mg / L~1.25 mg / L, and the concentration of
brassinolide is 0.025 μg / L~0.050 μg / L. The fruit enlargement agent of this invention, combined with fruit
thinning treatment, can increase the weight of a single Daqing
grape berry by at least 20% while retaining the
soluble solids content of the grape.