Abstract: This is an essay in the field of mineral analysis. In recent years, Chinese geological researchers have discovered a new type of sedimentary rare earth ore in Yunnan and Guizhou regions, which is not only different from bastnaesite and monazite, but also different from ionic rare earth ore in south of China, but a unique rare earth ore in clay rocks. In this paper, the ore dissolution methods of two rare earth samples with different grade from different mineral sites in adjacent areas of Yunnan and Guizhou are compared, and the distribution of key rare earth elements（Pr、Nd、Tb、Dy）, the optimization of instrument parameters and the accuracy and precision of the determination method of key rare earth elements are studied in detail. The results show that the closed digestion system is the best method for the new deposit of rare earth ore, and ICP-MS is an accurate and efficient determination method with good precision and accuracy.