The invention discloses a dapagliflozin impurity synthesis method. The synthesis method includes: using D-glucose as a raw material; subjecting the D-glucose to reactions of aldehyde group protection through ethanethiol, benzyl group adding, ethanethiol removal, condensation and benzyl group removal to obtain dapagliflozin impurities. A basis is provided for study of dapagliflozin related substances.