The Williamson synthesis method is a method for preparing asymmetric ethers, which is obtained by the reaction of halogenated hydrocarbons with sodium alcohol or sodium phenol. According to literature research, the influencing factors of this reaction include halogenated hydrocarbons, alkylated alcohols, catalysts, solvents, and side reactions; In addition, this method can be used to introduce various substituents such as saturated, unsaturated, aliphatic, and aromatic hydrocarbon groups in drug synthesis, thereby obtaining a variety of pharmaceutical intermediates or drugs. This article selects the antitumor drug gefitinib involved in this reaction as a case study to illustrate the complete synthesis route of this drug. Other reaction types and names involved in the drug synthesis route are also described.