The invention discloses a preparation method of ammonium tungsten oxide sulfide. The method belongs to the field of high-purity chemical preparation. According to the method, tungsten compounds and solid vulcanizing agents take reaction in a water solution; ammonia gas generated in the reaction process is exhausted out from reaction liquid into the reaction liquid in a mode of vacuum pumping or insert gas inflation in the reaction process; the movement of the reaction balance in the direction of the product ammonium tungsten oxide sulfide is promoted; a proper amount of ammonium salt is added into the reaction liquid; the separation of the product of the ammonium tungsten oxide sulfide is promoted; the high-purity ammonium tungsten oxide sulfide is prepared at high yield. The method has the advantages that little waste is discharged; the use of irritant ammonium hydroxide and ammonium sulfide solution and virulent and effluvial hydrogen sulfide gas is not needed; the process conditions are simple; the environment-friendly effect is achieved; the yield is as high as more than 98 percent, and the like. By using the method according to the invention, the gram level to ton level of ammonium tungsten oxide sulfide products can be efficiently produced; the industrialized mass production can be easily realized.