The invention provides a method for synthesizing chlorinated formic acid 9-fluoren methyl, which comprises the following steps: (1) 9-fluoren methyl and triphosgene are reacted for 0.5 to 3 hours in ice bath, under the existence of catalyst and in organic solvent; the catalyst is chosen from N with nucleophilicity, N-dimethylformamide, acetone, diisopropyl ethyl amine, diethylamine, triethylamine, ethyleendiamine, putrescine, imidazole, and the solvent is chosen from benzene, toluene, cyclohexane, hexane, heptane, cyclopentane, dichloromethane, chloroform and the compound thereof; (2) the temperature raises to 20 to 50 DEG C, and the mixture reacts for 1 to 5 hours. The method for synthesizing chlorinated formic acid 9-fluoren methyl adopts safe solid phosgene as reactant, and is simple in technique, convenient in safety, mild in condition, high in yield and easy in realization of industrialization production; the solvent can be used repeatedly after being processed simply, and the products do not need to be refined, and purity is up to more than 98 percent.