The invention discloses a preparation method of a praseodymium-neodymium alloy. The preparation method comprises the following steps that S1, a praseodymium-neodymium fluoride and lithium fluoride areevenly mixed according to the ratio of the praseodymium-neodymium fluoride to the lithium fluoride being (8-10):1 and then serve as an electrolyte, an electrolytic furnace is subjected to temperatureincreasing in an arc-striking mode, the electrolyte is added into a molybdenum crucible of the electrolytic furnace along with the temperature increasing process, and the electrolyte is molten through the electrolytic furnace; S2, a high-temperature-resistant anode is inserted into the electrolytic furnace, a direct current is guided into the electrolytic furnace through the high-temperature-resistant anode, and thus the current density of the anode is 0.1-1.5 A/cm<2>; S3, when the temperature of the electrolytic furnace is increased to be 1000-1100 DEG C, a tungsten cathode is inserted, a rectifier is started, the current density of the cathode is 6-20 A/cm<2>, and meanwhile, a praseodymium-neodymium oxide is added into the electrolytic furnace; and S4, the praseodymium-neodymium oxide is electrolyzed in the electrolytic furnace, praseodymium-neodymium metal is separated out from the tungsten cathode, after electrolyzing is completed, the molybdenum crucible is mechanically lifted out, molten metal is poured into a metal mold, and after cooling, a praseodymium-neodymium alloy ingot is formed. The high-temperature-resistant anode is prepared from nano graphite powder and a porousceramic material.