Abstract: The Hailuoling deposit, which is located in Shicheng County, southern Jiangxi, is a granitic pegmatite-type Nb-Ta-Zr-W-Sn-Li-Rb polymetallic deposit formed in the Mesozoic. Previous studies have focused on the geological characteristics of the deposit, but have not elucidated its formation mechanism yet. This research analyzed the micas in the fine-grained albite granite, greisenized granite, greisen, and pegmatite in the Hailuoling deposit by electron probe microanalysis (EPMA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The results show that micas in the fine-grained albite granite are dominated by lepidolite and zinnwaldite. In greisenized granite and greisen, micas are composed of protolithionite. The micas in pegmatite are mainly zinnwaldite and protolithionite. These rocks did not evolve according to the order of gradual increase of lithium content from granite → greisenized granite → greisen → pegmatite. Furthermore, compared to the greisenized granite and greisen, the micas in the fine-grained albite granite contain higher Rb, Li, and F but a lower K/Rb ratio. The regularity of major and trace elements possibly indicates a product of a more intense fractionation process of the same magmatic source. The sieve-like textures in the pegmatite suggested that the deposit experienced a transition from slow nucleation in the early stage to rapid undercooling in the later stage. By comparing the characteristics of the deposits and minerals in pegmatite between Hailuoling deposit and Koktokay deposit, it is inferred that the two deposits have similar ore-forming mechanism. Both of them experienced crystal fractionation dominated by melts, fluid exsolution, and the coexistence of melts and fluids. Some minerals crystallized under slow undercooling and solidified under rapid cooling conditions during the emplacement of the melt-fluid coexistence system, forming the granitic pegmatite-type deposit far away from the magma chamber and characterized with a mixture of various rock types.