A method for preparing xanthate by a slurry method includes steps of: adding a mixture of dichloromethane and carbon disulfide as a reaction solvent in a slurry reactor, and then adding alcohol and caustic alkali to react with carbon disulfide under less than 1 atm to remove heat released by the reaction by evaporating the solvent; performing vacuum distillation after the reaction to remove the solvent and water, so as to obtain the xanthate; transporting the xanthate to a granulation equipment for granulating, and then drying in a drying equipment to obtain a product. The method is performed in a system formed by a reaction equipment, a solvent recovery equipment, the granulation equipment, and the drying equipment, wherein a main equipment of the reaction system is a slurry reactor. The method has advantages of high efficiency, low energy consumption, good safety, environmental friendliness, convenient operation and the like.