The invention provides a method for synthesizing a fluorine-containing pyrimidinone compound, and belongs to the field of organic synthesis. The method does not use a metal reagent and an organic solvent, is environmentally friendly, and is suitable for industrial production. The method comprises the following steps: separately adding the pyrimidinone compound and sodium trifluoromethylsulfinate into a reaction flask for reacting under the action of tert-butyl peroxybenzoate (TBPB) and water at temperature of 25 DEG C to 80 DEG C for 2 to 4 hours; and after completion of the reaction, performing column chromatography to obtain the fluorine-containing pyrimidinone compound. The method can be applied to the synthesis of a trifluoroalkyl-substituted pyrimidinone compound.