The utility model relates to the technical field of desulfurization wastewater treatment, in particular to a device for reducing the chloride ion concentration of desulfurization wastewater. The device comprises a gypsum cyclone, a wastewater cyclone, a vacuum dehydration belt conveyor, a filtrate tank and a wastewater feeding tank, a feeding pipe is fixedly connected to the middle feeding end ofthe gypsum cyclone, and the bottom discharging end of the gypsum cyclone is fixedly connected with the feeding end of the vacuum dehydration belt conveyor through a first pipeline. The device is reasonable and compact in structure; convenient use, a gypsum cyclone, a wastewater cyclone, a vacuum dehydration belt conveyor, a filtrate tank and a wastewater feeding tank are matched for use; the purpose of effectively reducing the concentration of chloride ions in limestone-gypsum wet desulphurization slurry is achieved, scaling of gypsum and damage and corrosion to desulphurization equipment areprevented, the desulphurization efficiency and the gypsum quality are improved, the production cost is reduced, and meanwhile zero discharge of wastewater is achieved.