The invention relates to a Dapagliflozin preparation method, which comprises the following steps: using 2-chlorobenzaldehyde as a starting material, carrying out bromination, reducing, chlorinating tosynthesize 5-bromo-2-chlorobenzyl chloride, carrying out Friedel-Crafts alkylation reaction between 5-bromo-2-chlorobenzyl chloride and phenetole to synthesize 5-bromo-2-chloro-4'-ethyoxyldiphenylmethane, conducting condensation between 5-bromo-2-chloro-4'-ethyoxyldiphenylmethane and 2,3,4,6-tetra-O-trimethylsilyl-D-glucolactone, carrying out trimethylsilyl deprotection, conducting etherification, and reducing for demethylation to obtain a hypoglycemic drug Dapagliflozin. The invention has the following advantages: according to the Dapagliflozin preparation method, 2-chlorobenzaldehyde, whichis used as a starting material, is cheaper and easily available in comparison with 5-bromo-2-chlorobenzoic acid, and the technology is easy for industrialization; during the synthetic process, no rawmaterials which cause severe toxicity will be used and furthermore there is no dangerous process; the synthetic route is short and novel and the operation is simple; and through the synthetic route,purity of the final product can be raised, and the purity can reach 99% and above.