Abstract: Upper Permian Longtan Formation clay rocks, which are related to the weathering of Permian Emei basalt, are widely distributed in the middle zone and outer zone of Emei Large Igneous Province of Southern Sichuan, and they have geological background and metallogenic conditions for the formation of rare earth and other critical metal mineral resources. A systematic geological survey has been carried out in the lower part of Upper Permian kaolinitic clayston Longtan Formation in Changning anticline, and REE content in clay rocks was analyzed. The results show that the types of clay rocks (ore) include kaolinite clay rocks, pyrite bearing kaolinite clay rocks and carbonaceous kaolinite clay rocks. The content of ω(TRE₂O₃) in clay rock samples ranges from 0.031% to 0.409% (with average of 0.098%), and the mineralization coefficient is 0.61~8.19, with the mineralization rate up to 85%, indicating good prospecting potential. The REE content and mineralization coefficient are the highest in pyrite bearing kaolinite clay rocks, which are the main lithologic assemblages for REE enrichment. The samples are LREE enrichment type, with moderate negative Eu anomalies and weak positive Ce anomalies. The stratigraphic contact and rare earth elements characteristics indicate that the source materials are mainly from Emei basalts, and a small amount of medium-acid rocks in Emei Large Igneous Province. The enrichment process of rare earth elements includes the initial enrichment formed by Emei basalt weathering, and further migration, adsorption and precipitation of rare earth elements under the oxidation-reduction environment of sea and land interaction, and then the enrichment and mineralization. The discovery of the enrichment of rare earth elements in the clay rocks of the lower part of Longtan Formation in Xingan area has guiding significance for the strategic prospecting.