Abstract: To develop lanthanum oxide certified reference materials and supplement and improve the system of rare earth reference materials.The samples are prepared by the solution doping method using lanthanum oxide as the raw material.Disperse lanthanum oxide raw materials in an organic solvent and add standard solutions in accordance with the composition design requirements.The development of the reference material was completed through a series of processes, including stirring volatilization in a constant-temperature water bath, evaporation, calcination at 850 ℃ for 2 hours, ball milling, mixing, preliminary homogeneity inspection, packaging, stability testing, homogeneity verification, mathematical statistics and value assignment.The standard value of certified reference materials is 38 elements,including 14 kinds of rare earth oxide,ThO₂,Sc₂O₃,TiO₂,V₂O₅,Co₂O₃,NiO,CuO,Rb₂O,SrO,CdO,PbO,As,BaO,ZnO,P₂O₅,SiO₂,Al₂O₃,Cr₂O₃,MnO₂,MgO,Fe₂O₃,CaO,SO₄^2-,Cl^-.Eight laboratories with rich experience and strong technical ability in the field of rare earth detection were invited to use reliable analytical methods to determine the certified values and expanded uncertainties of lanthanum oxide certified reference materials.The certified reference materials has further improved and enriched the rare earth standard sample series in the field of nonferrous metals at home and abroad, and has been submitted to the State Administration for Market Regulation, National Standardization Administration for approval as a national standard sample.