After separating praseodymium from other rare earth elements through ion exchange or solvent extraction technology, metal praseodymium can be prepared by metal thermal reduction method. The lithium thermal reduction of rare earth chlorides is different from the Calciothermic reaction of rare earth chlorides. The reduction process of the former is carried out in the gas phase. The lithium thermal reduction reactor is divided into two heating zones, and the reduction and distillation processes are carried out in the same equipment. Anhydrous Praseodymium(III) chloride is placed in the upper titanium reactor crucible (also known as PrCl3 Still room), the reducing agent lithium is placed in the lower crucible, and then the stainless steel reaction tank is vacuumized to 7Pa before heating. When the temperature reaches 1000 ℃, maintain for a certain period of time to allow PrCl3 vapor to fully react with lithium vapor, and the reduced metal praseodymium solid particles fall into the lower crucible. After the reduction reaction is completed, only heat the lower crucible and distill LiCl into the upper crucible. The reduction reaction process usually takes about 10 hours. In order to obtain a relatively pure metal praseodymium, the reducing agent metal lithium needs to use 99.97% high-purity lithium and anhydrous PrCl3 from secondary distillation.