Though significant research progress has been made on REE in the Nb- REE polymetallic enrichment layer in Yunnan, in the Guizhou region of Late Permian Xuanwei Formation, several larger questions remain to be addressed. This study focusses the bottom of the Xuanwei Formation Nb- REE polymetallic enrichmentin the Muchuan area to investigate its formation mechanism and enrichment regularity. Field investigations, systemic mineralogical, lithofacies, paleogeographic, and rock geochemistry studies have been undertaken to discuss the content source and enrichment regularity to establish a metallogenic model. The results showed that the Nb- REE polymetallic enrichment layer at the bottom of the Xuanwei Formation in the Muchuan area, southern Sichuan has a thickness of 5. 09~15. 33 m and an average thickness of 10. 10 m. The content of niobium oxide (Nb2O5) was 37. 0~909 μg/g, with an average of 256 μg/g. The total amount of rare earth was 200~15500 μg/g, with an average of 1200 μg/g. The provenance of Nb- REE polymetallic enrichment layer mainly comes from the basalt of Mount Emei. In addition, the alkaline volcanic ash ejected at the mantle plume stage of Mount Emei may also provide some provenance. Independent rare earth minerals are rare, and the occurrence state of rare earth elements may be mainly in clay minerals in the form of similar- image substitution. No independent niobium minerals have been found, and the enrichment of niobium may be mainly related to anatase. The lower purple red iron mudstone belongs to the eluvial plain facies, the overlying gray white and light gray green aluminum mudstone belongs to the relatively calm lakeside subfacies environment, while the upper gray mudstone and dark gray carbonaceous mudstone belong to the relatively calm shallow lake subfacies environment. The enrichment degree of rare earth elements in purplish red ferritic mudstone is higher than that of niobium.The variation curve of niobium and rare earth element content in the upper gray white, light gray green, gray and dark gray mudstone shows the rule of "increase with the same decrease".The metallogenic model of Nb- REE polymetallic enrichment layer in Muchuan area can be divided into four stages: Emeishan basalt gusher stage, weathering enrichment stage, sedimentary accumulation stage and capping deposition stage. The mineralization is dominated by weathering leaching and deposition. The above results are of great significance to the key metal prospecting and the improvement of the Emeishan igneous mineralization system in Southwest China.