A florfenicol synthesizing method, comprising the following steps: dissolving 2-bromo-3-chloro -1-[4-(methylmercapto) phenyl]-1-acetone in an organic solvent, adding an oxidation catalyst and hydrogen peroxide to prepare 2-bromo-3-chloro-1-[4-(methylsulfonyl) phenyl]-1-acetone; dissolving the 2-bromo-3-chloro-1-[4-(methylsulfonyl) phenyl]-1-acetone, chiral amine of R 1 -NH 2 and alkali in an organic solvent, reacting at 0 to 30 DEG C to prepare a chiral aminoketone compound of a diastereoisomer, and performing a physical separation method on the chiral aminoketone compound of the diastereoisomer to obtain an R-configuration aminoketone compound 1: 1-R1-2- -[4-(methylsulfonyl) phenyl] formyl aziridine; wherein R 1 is -1-phenethyl or -1-phenethyl; dissolving the 1-R 1 -2- -[4-(methylsulfonyl) phenyl] formyl aziridine in an organic solvent, cooling, and then reacting with a hydride reagent and Lewis acid to obtain a single-configuration chiral aminoketone compound 2: -[4-(methylsulfonyl) phenyl] [ -1-R 1 -aziridin-2-yl] methanol; heating the -[4-(methylsulfonyl) phenyl] [ -1-R 1 -aziridin-2-yl] methanol and triethylamine trihydrofluoride in an organic solvent to obtain (1S, 2S)-3-fluorine-1-[4-(methylsulfonyl) phenyl]-2-(R 1 -amino)-1-propanol; performing the hydrogeneration protection for the (1S, 2S)-3-fluorine-1-[4-(methylsulfonyl) phenyl]-2-(R 1 -amino)-1-propanol in an organic solvent via Pd/C to obtain (1S, 2S)-2-amino-3-1-[4-(methylsulfonyl) phenyl]-1-propanol; acetylating the (1S, 2S)-2-amino-3-1-[4-(methylsulfonyl) phenyl]-1-propanol with an acetylation reagent having a group R, and cyclizing the acetylated compound in the presence of a sulfonic acid or sulfonyl chloride esterification reagent to prepare a compound 3, and performing the hydrolysis and the acetylation on the compound 3 to obtain florfenicol; wherein R 2 is phenyl or bischloromethyl or hydroxy. dissolving 2-bromo-3-chloro -1-[4-(methylmercapto) phenyl]-1-acetone in an organic solvent, adding an oxidation catalyst and hydrogen peroxide to prepare 2-bromo-3-chloro-1-[4-(methylsulfonyl) phenyl]-1-acetone; dissolving the 2-bromo-3-chloro-1-[4-(methylsulfonyl) phenyl]-1-acetone, chiral amine of R 1 -NH 2 and alkali in an organic solvent, reacting at 0 to 30 DEG C to prepare a chiral aminoketone compound of a diastereoisomer, and performing a physical separation method on the chiral aminoketone compound of the diastereoisomer to obtain an R-configuration aminoketone compound 1: 1-R1-2- -[4-(methylsulfonyl) phenyl] formyl aziridine; wherein R 1 is -1-phenethyl or -1-phenethyl; dissolving the 1-R 1 -2- -[4-(methylsulfonyl) phenyl] formyl aziridine in an organic solvent, cooling, and then reacting with a hydride reagent and Lewis acid to obtain a single-configuration chiral aminoketone compound 2: -[4-(methylsulfonyl) phenyl] [ -1-R 1 -aziridin-2-yl] methanol; heating the -[4-(methylsulfonyl) phenyl] [ -1-R 1 -aziridin-2-yl] methanol and triethylamine trihydrofluoride in an organic solvent to obtain (1S, 2S)-3-fluorine-1-[4-(methylsulfonyl) phenyl]-2-(R 1 -amino)-1-propanol; performing the hydrogeneration protection for the (1S, 2S)-3-fluorine-1-[4-(methylsulfonyl) phenyl]-2-(R 1 -amino)-1-propanol in an organic solvent via Pd/C to obtain (1S, 2S)-2-amino-3-1-[4-(methylsulfonyl) phenyl]-1-propanol; acetylating the (1S, 2S)-2-amino-3-1-[4-(methylsulfonyl) phenyl]-1-propanol with an acetylation reagent having a group R, and cyclizing the acetylated compound in the presence of a sulfonic acid or sulfonyl chloride esterification reagent to prepare a compound 3, and performing the hydrolysis and the acetylation on the compound 3 to obtain florfenicol; wherein R 2 is phenyl or bischloromethyl or hydroxy.