This standard specifies a method for the determination of cerium content in lanthanum-cerium metal and its compounds using the Titrimetric method of ammonium ferrous sulfate. It is suitable for the determination of the mass fraction of cerium in lanthanum-cerium metal and the content of cerium oxidation in lanthanum-cerium oxidation, lanthanum-cerium carbonic acid and lanthanum-cerium chloride. The standard details the operation steps of dissolving the sample, oxidizing cerium with perchlorate in phosphoric acid medium, and determining the cerium content by titration. This method provides an important analytical means for the quality control of related materials and is suitable for the chemical analysis of rare earth elements.