The invention relates to a synthesis method of celecoxib, which comprises the following specific steps of: 1, carrying out claisen condensation on p-methylacetophenone and trifluoroacetic acid ethyl esters in an aprotic organic solvent under the catalysis of alkali to obtain 1-(4-methylphenyl)-4,4,4-trifluoro-1,3-butanedione; and 2, reacting the obtained 1-(4-methylphenyl)-4,4,4-trifluoro-1,3-butanedione with sulfonamide-phenylhydrazine hydrochloride to obtain celecoxib, wherein in the step 1, the alkali for catalysis is selected from one or more of sodium hydride, potassium hydride, lithium hydride and calcium hydride. The synthesis method of celecoxib provided by the invention is easy to operate, high in yield, high in product purity and easy for industrial production.