The invention provides a reagent for accelerating Fenton reaction as well as a preparation method and application of the reagent. The reagent for accelerating the Fenton reaction is copper carbon dot CuCD, and the preparation method comprises the following steps: S1, mixing 3, 4-dihydroxyphenylpropionic acid and copper chloride, dissolving the mixture with deionized water, uniformly stirring, adding 2, 2'-(ethylenedioxy) diethylamine, and performing stirring; S2, transferring the solution obtained in the step S1 into a reaction kettle, reacting at 170-190 DEG C for 4-6 hours, and performing cooling to room temperature; S3, centrifuging the solution after the reaction in the step S2, enabling the solution to pass through a water-phase filter membrane, then putting the filtrate into a dialysis bag for dialysis, and freeze-drying to obtain the copper-carbon dots CuCD. The reagent for accelerating the Fenton reaction can be combined with a Fenton reagent, is applied to treatment of organic matters in water, has good biological safety, can accelerate the reaction rate of the Fenton reagent, improves the degradation rate of pollutants in wastewater, and accelerates the oxidation rate of 3, 3', 5, 5'-tetramethyl benzidine.