The invention relates to a vacuum preparation system of xanthate and belongs to the technical field of chemical engineering. The system comprises a mill feed pipe, a mill, a mill discharge pipe, a fan, an air pipe, a high-pressure transmitter, a high-pressure air pipe, a feed pipe and reaction liquid containers, and further comprises a feed system, a vacuum synthesizer, a discharge pipe, a finished product bin, a cold water layer and a refrigerant water supply system; xanthate is produced in a vacuum environment; a reaction of oxidizing ions with oxygen or carbon dioxide and the like in air inan xanthate production reaction process is effectively avoided; the purity of xanthate is improved; at the same time, many stirring rods are uniformly distributed on two stirring shafts; after synthesis liquid is added into a synthesis case, vigorous stirring can be achieved; mutual contact between materials is enhanced; alkali can be mixed with the synthesis liquid timely and uniformly; automatic feed of sodium hydroxide is achieved at the same time; and refrigerant water is supplied centrally.