The invention discloses high-specific-activity tritium-labeled zaltoprofen and a preparation method thereof, and belongs to the technical field of medicine preparation. According to the method, 2-(3-carboxymethyl-4-phenylthiophenyl)methyl propionate is used as a raw material, and is subjected to three-step reaction of bromine substitution, dehydration condensation and hydrolysis to generate 4-bromo zaltoprofen, the 4-bromo zaltoprofen and tritium gas are subjected to tritium-halogen exchange under the actions of a palladium-carbon catalyst and an alkali acceptor to prepare 4-<3>H-zaltoprofen,and the synthesized product is subjected to preparation liquid phase purification to obtain tritium-labeled zaltoprofen with high specific activity (29.30 ci/g), high radiochemical purity (greater than or equal to 98%) and high chemical purity (greater than or equal to 99%). According to the invention, the prepared 4-<3>H-zaltoprofen provides a material basis for researching the absorption, distribution, metabolism and excretion of zaltoprofen in an animal body.