Production line equipment for preparing a high-purity magnesium alloy through continuous vacuum smelting comprises a vacuumizing assembly, a control mechanism, a heating volatilization furnace, a magnesium steam filter device, a cooling crystallizer, a vacuum receiver, a crystal melting furnace, an alloy melting furnace and an alloy forming device, wherein the control mechanism, the heating volatilization furnace, the magnesium steam filter device, the cooling crystallizer, the vacuum receiver, the crystal melting furnace, the alloy melting furnace and the alloy forming device are connected with the vacuumizing assembly. The vacuumizing assembly can carry out vacuumizing treatment on the interiors of the heating volatilization furnace, the magnesium steam filter device, the cooling crystallizer, the vacuum receiver, the crystal melting furnace, the alloy melting furnace and the alloy forming device under control of the control mechanism. Through the improvement of the structures of thecooling crystallizer, the vacuum receiver, the crystal melting furnace and the alloy melting furnace in the magnesium alloy production line equipment, the equipment can rapidly, efficiently, safely and automatically complete production of the ultrahigh-purity magnesium alloy under the conditions of whole-process vacuum and inert gas shielding so as to prepare the high-purity magnesium alloy withhigh quality and mass.