This standard specifies the determination method for the content of molybdenum, tungsten and titanium in rare earth ferroalloys (including lanthanum ferroalloys, cerium ferroalloys, neodymium ferroalloys, etc.). The applicable determination range is 0.010%~ 0.20% of tungsten, 0.005%~ 0.10% of molybdenum, and 0.005%~ 0.10% of titanium. The sample is dissolved by nitric acid and hydrofluoric acid, and the rare earth matrix is separated by fluorination. Light spectrum analysis is performed using an argon plasma light source to determine the content of molybdenum, tungsten and titanium. The standard ensures the accuracy in the determination process and specifies the purity requirements of the reagents and materials required for analysis.