The invention discloses a preparation method for hypoglycemic drugdapagliflozin. The method comprises the steps that 4-hydroxybenzaldehyde is adopted as a starting raw material, alkylation, carbonyl reduction, chlorination and alkylation reaction with asepsin, diazotization and chlorination are performed to obtain a dapagliflozinmidbody 5-bromo-2-chloro-4'-ethyoxyl diphenylmethane, then, the midbody and 2,3,4,6-tetra-O-trimethyl silicone-D-glucolactone are subjected to condensation, etherification and methoxyl removal to obtain the hypoglycemic drugdapagliflozin. The raw materials adopted by the technological path are low in price and easy to obtain, the technology can achieve industrialization easily, and the final product is high in purity; the technological path is novel, the syntheticroute is short, no risky or complex technology exists in the reactions, equipment is simple, operation is easy and convenient, and the method is suitable for industrial production.