After separating lanthanum from other rare earth elements through ion exchange or solvent extraction technology, metallic lanthanum 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 Lanthanum(III) chloride is placed in the upper titanium reactor crucible (also known as LaCl3 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 LaCl3 vapor to fully react with lithium vapor, and the solid particles of reduced metal lanthanum 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 pure lanthanum metal, the reducing agent lithium metal needs to use 99.97% high-purity lithium and anhydrous LaCl3 from secondary distillation.