The Taoxikeng tungsten deposit is a large wolframite deposit in southern Jiangxi Province. In order to reveal the early evolution characteristics of ore- forming fluids and the enrichment mechanism of tungsten, we carried out study of fluid and melt inclusions in greisen by means of petrography, laser Raman spectroscopy and microthermometric experiments. The results show that fluid inclusions can be divided into three types: liquid- rich two- phase aqueous inclusions, vapor- rich CO2- bearing inclusions and pure gas inclusions. The ore- forming fluids are characterized by medium- high temperature, low salinity and low density, roughly belonging to NaCl- H2O- CO2- CH4 system. Melt inclusions are mainly composed of albite, quartz, with minor amount of fluid and gas, and gas phase contains CH4 and trace CO2. In the early stage of magmatic hydrothermal evolution, the redox conditions of the fluid might have been changed, resulting in a shift of CH4 to CO2 and an increase in CO2 content of the fluid. Fluid immiscibility, which is characterized by the dissipation of CO2, could be the main mechanism responsible for the formation of the Taoxikeng tungsten deposit. Carbon dioxide plays a significant role in the migration and enrichment of tungsten, and the dissipation of CO2 component is one of the important factors that induce the precipitation and enrichment of wolframite.