The method discloses a synthesis method of tungsten hexafluoride, comprising the following steps: putting tungsten powder and metal fluoride into a reactor, sufficiently mixing, introducing fluorine under a reaction condition, reacting to synthesize the tungsten hexafluoride, enabling the raw material fluorine which is not completely reacted and the product tungsten hexafluoride to be subjected tocondensation gas liquid separation, and then returning to the reactor for circular reaction. According to the synthesis method, the circulated fluorine and tungsten powder are used for reacting in the presence of the metal fluoride, the reaction efficiency is effectively improved, the waste of the raw material fluorine is reduced, and the needed size of the reactor is effectively reduced.