A synthesis method for 4,4,4-trifluoro-1- (4-methylphenyl)-1,3-butanedione was provided. Starting from 4'-methylacetophenone and ethyl trifluoroacetate, tetrahydrofuran was used as the reaction solvent, and the Claisen condensation reaction was carried out in the presence of 30% sodium methoxide catalyst. After the reaction of the raw materials was completed by high-performance liquid phase detection, the reaction solution was concentrated to remove tetrahydrofuran to obtain an oily substance. The pH vaule was adjusted to 1~2 with 10% hydrochloric acid, and then extracted with ethyl acetate. Dry with anhydrous sodium sulfite, filter and concentrate to remove ethyl acetate to obtain the oily 4,4,4-trifluoro-1- (4-methylphenyl) butane-1,3-dione. The yield of the entire process is over 96%, and the purity is as high as 99.44%. The synthesis process route is simple, and the post-treatment is convenient and easy to operate, making it very suitable for industrial production.