The invention discloses a synthetic method of 2, 4-dichlorofluorobenzene. The method comprises the following steps: 1,2,4-trichlorobenzene is used as a raw material, a calix[6]arene and trimethylolpropane borate compound is used as a phase transfer catalyst, spray-dried potassium fluoride is used as a fluorinating agent, and the 2,4-dichlorofluorobenzene is produced through one step of reaction; herein, the molar ratio of trimethylolpropane borate to potassium fluoride is 1:10-1:20, preferably 1:15; the molar ratio of the potassium fluoride to the 1,2,4-trichlorobenzene is 1:1.1; the calix[6]arene is p-tert-butyl calix[6]arene; and the molar ratio of the p-tert-butyl calix[6]arene to the 1,2,4-trichlorobenzene is 0.001:1-0.05:1, preferably 0.02:1. By using the calixarene and trihydroxymethyl borate composite catalyst, the catalytic efficiency is greatly improved, and the product yield is as high as 92%. The boiling point of the 2,4-dichlorofluorobenzene is 168-169 DEG C, the boiling point of the raw material 1,2,4-trichlorobenzene is 214 DEG C, and the boiling point of the solvent sulfolane is 285 DEG C, so that the product is simple to separate and purify. The method has the advantages of one-step synthesis, short reaction route, avoidance of nitrification and high-temperature chlorination, safer synthesis process and suitability for industrial production.