The Tiegelongnan deposit yields the largest porphyry-high sulfidation Cu (Au, Ag) mineralization system in the Bangong-Nujiang metallogenic belt of Tibet. The advanced argillic alteration was widely imposed on the phyllic zone resulting in a complex mineralization process and metallogenic system that impedes the construction of an accurate metallogenic model. Based on the previous exploration and research on the Tiegelongnan deposit, we mainly focus on the typical alteration mineral (muscovite). With the objective of studying the metallogenic mechanism of the Tiegelongnan deposit, we investigate its mineralogical characteristics under scanning electron microscope and electron microscope, and uncover the genesis of muscovite which was produced in different conditions and locations. Finally, the significance of the mineralization mechanism is discussed with all the geochemical analyses. It is proved that the muscovite of the Tiegelongnan deposit is composed of muscovite, illite and celadonite endmembers as well as minor paragonite endmembers. In the ore-body muscovite and copper minerals have a close paragenetic link. In the early-stage water-rock interactions in deep levels, high Si and low Al muscovite-chalcopyrite were produced in porphyries, while high Al and low Si muscovite-chalcopyrite formed in sandstone. With the progression of hydrothermal evolution towards shallower levels, the sulfides graded to bornite and covellite and the muscovite with high Al and low Si content was produced. Besides, muscovites from the altered sandstones are also enriched in FeT, Fe3+, Na+ compared to those present in intrusions. Fe2+-rich muscovite in porphyries indicates a reduced hydrothermal condition. In the medium-shallow level of the phyllic alteration zone of the Tiegelongnan deposit, muscovites frequently occur with a certain amount of kaolinite as well as bornite and covellite, which reflects that the SO2 enrichment, temperature decrease and acid increase resulted in a stronger water-rock interaction and copper precipitation. All in all, different mineral assemblages concerning with muscovite and the distinct muscovite geochemical characteristics have important implications for the hydrothermal conditions and the exploration prospecting.