To investigate the ore- forming fluid characteristics, evolution and genesis of the tungsten polymetallic deposits in the southern part of Sanjiang Tethyan, the Damajianshan tungsten polymetallic deposit in Lvchun, Yunnan, southwest China were selected as the research object. We carried out a detailed petrographic, microthermomertic and laser Raman spectroscopy study of the primary fluid inclusions in the copper mineralization and tungsten mineralization quartz veins from 512 m to 889 m level of the Damajianshan deposit. The results indicate that (i) the types of fluid inclusions are mainly gas- liquid phase inclusions (type Ⅰ), with a few subcrystal- bearing inclusions (type Ⅱ), and methane- rich inclusions (type Ⅲ), without pure gas- phase or pure liquid- phase inclusions; (ii) the homogenization temperature of fluid inclusions in copper mineralized quartz ranges from 165~335℃, and salinity from 4. 2%~16. 7% NaCleq; (iii) the homogeneous temperature of fluid inclusions in tungsten mineralized quartz veins ranges from 199 to 265℃, and salinity from 2. 6%~23. 7% NaCleq; (iv) there are a few daughter minerals dominated by stone salts; (v) the fluid solutes evolved gradually from NaCl, KCl, MgCl2 to CaCl2 with mineralization pressure of 17. 85~48. 90 MPa and depth of 0. 67~1. 85 km. The laser Raman spectroscopy indicates that the composition of the ore- forming fluid in each level of the Damajianshan deposit is similar, which are mainly H2O and CH4, with a small amount of N2 and trace amount of CO2. The homogeneous temperature of fluid inclusions is similar within the two kinds of mineralization at the same level, but the difference in salinity is large, and the CH4 and CO2 contents also differ significantly, which may have been caused by the evolution of copper mineralized fluids through the thermochemical sulfate reduction reaction (TSR) process, which is significantly different from the evolution of tungsten mineralized fluids. The participation of chloride plays a major role in the migration and enrichment of W elements in the Damajianshan tungsten polymetallic deposit; at the same time, it is controlled by the content of F- and Ca2+ as well as the activity product of manganocalcite and wolframite to form a scheelite- dominated tungsten body with scheelite above and wolframite below. From the deep to the shallow part of the orebody, the H and O isotope composition of the ore- forming fluid has changed significantly (showing a weak negative correlation). According to the evolutionary trend of H and O isotope composition during the process of water- rock reaction, it is inferred that the water- rock reaction is involved in the evolution of ore- forming fluid. Based on the above research results, it is concluded that the ore- forming fluid of the Damajianshan tungsten polymetallic deposit is composed of magmatic water and meteoric water, and the water- rock interaction occurred during the evolution process. During the migration and evolution of the ore- forming fluid, due to the change of temperature and pressure, the ore- forming fluid migrated outward with quartz porphyry as the main body, forming mineralization zones such as W and Cu- As around the rock body, the ore- forming materials precipitated to form tungsten polymetallic deposits.