The invention discloses a salt-out anti-blocking device for high-temperature salt out in multiple-effect negative-pressure evaporator. The salt-out anti-blocking device comprises a heater, a separatorand a thick kettle which are successively connected in sequence; a circulating pump is connected to a clear liquid outlet of the separator, the circulating pump is connected with a circulating liquidinlet of the heater, a steam outlet of the heater is connected with a steam inlet of the separator, and the heater, the circulating pump and the separator form a circulating evaporation system; a concentrated solution outlet of the separator is connected with a discharging pipeline, and connected with the thick kettle through the discharging pipeline; a heat supplying sleeve fixedly sleeves the discharging pipeline, and a containing space is enclosed between the discharging pipeline and the heat supplying sleeve; and heat flow passes through the containing space to supply heat for the discharging pipeline. According to the salt-out anti-blocking device, the problems that a concentrated solution flowing out of the separator is prone to crystallizing in the discharging pipeline due to the decreasement of the temperature or too high concentration or the delay of salt discharge due to shutdown in the process of flowing from the discharging pipeline to the thick kettle, and thus the concentrated solution is attached to the inner wall of the discharging pipeline and causes blockage of the pipeline can be solved.