Abstract: The Mufu Mountain area in the middle section of the Jiangnan Orogenic Belt is one of the important rare - metal resource bases in China. The Duangfengshan large - scale niobium - tantalum deposit is located on the northern margin of the Mufu Mountain pluton. In the early stage, numerous scholars carried out studies on the mineralogy of minerals such as garnet and niobium - tantalum ore, as well as geochronology, on the niobium - tantalum - bearing pegmatite veins in the Duangfengshan mining area, and considered this area to belong to the LCT - type pegmatite - type niobium - tantalum deposit. Through several years of mineral exploration work in the Duangfengshan mining area, one lepidolite - bearing pegmatite vein was discovered. This time, mineralogical and fluid inclusion studies were conducted on the lepidolite - bearing pegmatite and the niobium - tantalum - bearing pegmatite, and the formation differences were analyzed through comparison.In general, for the mica in the rare - metal pegmatites, the contents of Cs, Rb, and Li decrease as the K/Rb ratio increases. The lepidolite - bearing pegmatite vein has the lowest K/Rb ratio and the highest contents of Li, Cs, and Rb simultaneously. In the pegmatites, for the columbite - group minerals, with the increase in the degree of differentiation and evolution of the pegmatite, the Mn/(Mn + Fe) value first gradually increases, and then the Ta/(Ta + Nb) ratio increases, indicating that lithium mineralization is enriched only in the pegmatites in the late stage of crystallization differentiation. The test results of fluid inclusions show that the temperature of the No. 124 lepidolite - bearing pegmatite is lower than that of the No. 343 non - lepidolite - bearing pegmatite vein, indicating a higher degree of post - hydrothermal metasomatism.