The invention relates to the technical field of chemical synthesis, particularly to a duloxetine preparation method. The duloxetine preparation method comprises the following steps: choosing thiophene and 2-chloroacetyl chloride as raw materials, sealing and storing at 20-25 DEGC for standby application, putting 2-chloroacetyl chloride into a reaction vessel, heating to 60-65 DEGC, adding thiophene, slightly shaking evenly, continuing to heat, stirring for 10 minutes, obtaining 2-chloracetyl-thiophene through a friedel-crafts reaction, heating the produced 2-chloracetyl-thiophene to 80-100 DEGC, adding sodium cyanide into the reaction vessel, continuing to stir, heating for 10 minutes, conducting a cyano substitution reaction, and obtaining 3-hydroxy-3-(2-thiophene)-propionitrile. The cheap thiophene and 2-chloroacetyl chloride are chosen as the raw materials, the preparation is easy, the cost is low, the preparation is conducted through the conventional reactions, and the method has the advantages of low cost, easy preparation and high reaction speed.