This standard specifies a method for the determination of molybdenum and tungsten in rare earth metals such as lanthanum, cerium, and neodymium by Inductance-coupled plasma emission Light spectrum and Inductance-coupled plasma Mass spectrometry. The determination range is 0.010% to 0.50% each of molybdenum and tungsten. The sample is dissolved by nitric acid and hydrofluoric acid, and the rare earth matrix is separated for determination. The method has high Sensitivity and Accuracy and is widely used in the composition analysis and quality control of rare earth materials.