The invention discloses a tungsten hexafluoride synthesis method. The method includes: well mixing tungsten powder with metal fluorides in a reactor; feeding fluorine gas for reactive synthesis of tungsten hexafluoride; after condensation gas-liquid separation of unreacted raw material fluorine gas and product tungsten hexafluoride, returning to the reactor for circular reaction. By reaction of cyclic fluoride gas and tungsten powder in existence of the metal fluorides, reaction efficiency is effectively improved, waste of raw material fluorine gas is reduced, and required volume of the reactor is effectively decreased.