Abstract: The weathering crust ion adsorption rare earth ore sample was processed to 0.149 mm, and 35 g/L ammonium sulfate solution (pH 4.0) was used as the leaching agent to extract rare earth elements in the leaching phase. The effects of sample size, concentration and dosage of leaching agent, acidity of leaching agent, leaching method and leaching time on the extraction of rare earth elements in leaching phase were investigated. The optimal experimental conditions were determined. The total amount and component of rare earth elements in the leaching phase were determined by inductively coupled plasma mass spectrometry (ICP-MS). The experimental results showed that: the use of static leaching method for 30 min, with a solid-liquid ratio of 1∶10, can effectively extract rare earth elements in the leaching phase. The detection limit of rare earth elements was 0.006 5~0.160 0 μg/g respectively, the lower limit of determination was 0.035~0.520 μg/g, the precision was 1.34%~5.65%, and the recovery was 96.0%~102.0%. The results were accurate and reliable, and the method can fully meet the requirements of mineral geological exploration.