Direct rectification method of molten liquid crude cadmium

The invention discloses a direct rectification method of molten liquid crude cadmium. A cadmium cake is placed in a crude cadmium smelting furnace to be smelted, the smelting temperature ranges from 500 DEG C to 700 DEG C, the adding proportion of sodium hydroxide is (15-16):100, the adding proportion of a reducing agent is (1-2):100, and impurities Zn, Pb, Cu and NaOH react to generate sodium salt which is generally called alkali slag; the density of the alkali slag is smaller than that of cadmium, so that the alkali slag is layered and floats on cadmium liquid; meanwhile, a small amount of CdO wrapped by the alkali slag is reduced into metal cadmium by a reducing agent, the alkali slag is cleared up regularly to remove impurities, and a crude cadmium solution containing larger than 98% of Cd and smaller than 0.05% of Zn is obtained; the crude cadmium solution passes through the bottom of a crude cadmium smelting furnace, flows out of a discharging opening controlled by a valve special for groove-free metal