Abstract: The Guangxi Shanhu tungsten-tin deposit is a typical quartz vein-type tungsten-tin deposit in South China. In order to clarify the evolution of ore-forming fluid and the detailed mineralization process, LA-ICP-MS in-situ trace element analysis is carried out on muscovite in different mineralization stages of the deposit to constrain the mineralization process and mechanism. The results show that the mineralization process of the deposit can be divided into four stages: quartz-wolframite, quartz-sulfide, quartz-fluorite and scheelite-calcite. Two types of muscovite （Mic-1 and Mic-2） develop during the mineralization period. Mic-1 forms in the quartz-wolframite stage and coexisted with wolframite and cassiterite, while Mic-2 forms in the quartz-sulfide stage and coexists with sulfides. The two types of muscovite have similar geochemical characteristics, both significantly enriched in Li, B, Rb, Sn, Cs, Ba, medium in Be, V, Ga, Sr, W, Tl, and depleted in Co, Ni, Cu, Zr, Nb, In. The contents of Li, W and Sn in Mic-1 are significantly higher than those in Mic-2, indicating that the ore-forming fluid in the formation stage of Mic-1 has a higher proportion of magmatic hydrothermal components and a higher degree of differentiation and evolution. The massive crystallization of wolframite and cassiterite in the quartz-wolframite stage leads to the significant depletion of W and Sn in the fluid. The trace element characteristics of muscovite indicate that tungsten-tin mineralization formed in a hydrothermal environment with high oxygen fugacity and moderate pH value. The addition of atmospheric precipitation is a key factor in the evolution of ore-forming fluid, which increases the pH value of ore-forming fluid, reduces the solubility of tungsten, increases its saturation, and ultimately promotes the precipitation of tungsten from the fluid to form ore. The in-situ trace elements of muscovite can effectively trace the evolution process of the ore-forming fluid in the Shanhu tungsten-tin deposit, and provide mineralogical basis for analyzing the mineralization mechanism and guiding deep prospecting.