The invention discloses a synthetic method for 1,3,3,3-tetrafluoropropene. The synthetic method comprises the following steps: (1) adding a mixture of iodine, iodine pentafluoride and a catalyst into a reactor, controlling reaction temperature, introducing trifluoropropene, and stopping the reaction when system pressure is stable so as to obtain 1,3,3,3-tetrafluoro-2-iodopropane, wherein a mass ratio of iodine to iodine pentafluoride is 1: 0.4-0.5, a mass ratio of iodine to the catalyst is 1: 0.01-0.05, reaction temperature is -15 to 35 DEG C and reaction pressure is 0.1 to 0.6 MPa; and (2) evaporating the material 1,3,3,3-tetrafluoro-2-iodopropane in the reactor, introducing the evaporated 1,3,3,3-tetrafluoro-2-iodopropane into a reactor filled with alkali lye, carrying out a reaction at normal pressure, and subjecting a gas phase product to drying and compression so as to obtain the product 1,3,3,3-tetrafluoropropene, wherein reaction temperature is 35 to 80 DEG C. The method provided by the invention has the advantages of simple equipment, high operation security, high product purity, etc.