The invention discloses a siphon liquid discharging method for metallurgy. The siphon liquid discharging method comprises the following steps that one end of a high-temperature alloy pipe is slidablyinserted into a smelting furnace in a sealing manner, the other end of the high-temperature alloy pipe is connected into a heat preservation pool, and the height of the heat preservation pool is set to be less than that of the smelting furnace; the high-temperature alloy pipe and the heat preservation pool are vacuumized by using a vacuum pump for the first time; the vacuumized high-temperature alloy pipe and heat preservation pool are preheated through a heating device; a molten metal liquid in the smelting furnace is discharged from the high-temperature alloy pipe into the heat preservationpool through the siphon effect; the above high-temperature alloy pipe and heat preservation pool are vacuumized by using the vacuum pump for the second time, and the smelting furnace is pressurized byusing a pressurizing air pump in an auxiliary manner; and the height of the smelting furnace is adjusted by using a lifting platform, and/or the flow rate of the molten metal liquid in the high-temperature alloy pipe is adjusted by adjusting the height of the end, extending into the smelting furnace, of the high-temperature alloy pipe through a screw-nut mechanism. By adoption of the siphon liquid discharging method disclosed by the invention, the siphon flow rate of the molten metal liquid can be rapidly and conveniently adjusted to fit the processing speed of the next working procedure.