The present invention belongs to the casting technology. The continuous vacuum purifier includes mainly aluminum liquid electrolyser, purifying furnace and vacuum waste liquid recovering furnace, thealuminium liquid electrolyser is connected to the purifying furnace via ceramic pipe and the purifying furnace is connected to the vacuum waste liquid recovering furnace via ceramic pipe and cut-off valve. In the purification process, vacuum smelting and temperature maintaining avoids oxygen ion invasion, the pumping controls the solid-liquid interface in required range, the continuous addition of aluminium liquid reduces power consumption, and the waste aluminum liquid with relatively higher impurity density is produced into aluminum ingot directly.