Abstract: The age and tectonic setting of Eocene granites from Liemai in Longzi County, Tibet are of great significance to the tectonic evolution of the Himalayan region in the syncollision stage. In this paper, monazite LA-ICP-MS U-Th-Pb dating has been carried out for muscovite granites in Jieguidang. The weighted average age of ²⁰⁸Pb/²³²Th is 41 ±0.1 Ma (MSWD=1.4, n=40), which was formed in the Middle Eocene. Combined with the Eocene magmatic rocks and metamorphism in the region, it is considered that the middle high pressure metamorphism and partial melting occurred in the India lower crust at 50-45 Ma. The Neo-Tethys oceanic crust plate separated and the asthenosphere mantle upwelling occurred at 45 Ma. The Himalaya experienced a short-term extension environment, which resulted in a large number of adakitic magmatic rock emplacement and eclogite exhumation at 45-41 Ma.