The invention provides a mercury suction device. The mercury suction device comprises a gas supply pipeline, a Venturi generator, a collection bottle, a suction pipe and a compressed gas source, wherein one end of the gas supply pipeline is connected with the compressed gas source, the other end of the gas supply pipeline is connected with an inlet of the Venturi generator, and the compressed gas source is used for feeding compressed gas into the Venturi generator; a throat is arranged between the inlet of the Venturi generator and an outlet of the Venturi generator, a section between the inlet and the throat is an inlet section, a section between the outlet and the throat is an outlet section, and the cross-section area of the throat is separately smaller than that of the inlet section and that of the outlet section, so that the gas pressure of the throat is lowered when the compressed gas passes through the throat; a vent hole is formed in the inlet section and communicates with the top of the collection bottle, and gas in the collection bottle flows to the throat through the vent hole when the gas pressure of the throat is lowered; and a first end of the suction pipe is in sealed connection with the collection bottle, a second end of the suction pipe is located outside the collection bottle, and a second end of the suction pipe is used for sucking liquid mercury. According to the mercury suction device, the liquid mercury can be sucked continuously, the efficiency of suction is high, and the consumed time is short.