The Yiliu tungsten deposit, tectonically located in the southern margin of the central Nanling metallogenic belt and in the southwestern margin of the Quren basin in northern Guangdong, is one of the most important prospecting achievements of North Guangdong in recent years. It belongs to typical skarntype deposit, with ore bodies occurring in both skarn of the Upper Devonian Maozifeng Formation and NWWtrending Kfeldsparquartztungsten veins and micaquartz veins. Based on field and microscope observations, this study divides the oreforming process into skarn period (A) and hydrothermal period (B). The former is composed of early skarn stage (A1), late skarn stage (A2) and Kfeldsparquartztungsten stage (A3), whereas the latter is composed of micaquartz vein stage (B1) and quartzcarbonate stage (B2). Four types of fluid inclusions have been identified: daughter mineralbearing inclusions (type Ⅰ), gasaqueous twophase inclusions (type Ⅱ), threephase CO2aqueous inclusions (type Ⅲ) and pure CO2 inclusions (type Ⅳ). Type I occurs only in A3 stage quartz. Type Ⅱ, type Ⅲ and type Ⅳ can be found in A3 and B1 stage quartz, whereas twophase aqueous inclusions can be found in A3 and B1 stage tungsten. The homogenization temperatures of the type Ⅰ, type Ⅱ and type Ⅲ fluid inclusions in stage A3 vary from 162℃ to 381℃, 154℃ to 363℃ and 290℃ to 390℃, respectively. The salinities of type I inclusions range from 301% to 454%（wt%NaClequiv）, while those of type Ⅱ and type Ⅲ range from 149% to 110% and 220% to 688%. The homogenization temperatures of type Ⅱ and type Ⅲ fluid inclusions in B1 stage vary from 152℃ to 381℃ and 281℃ to 378℃, and the salinities of each type of inclusion ranges from 165% to 932% and 200% to 882%. Raman spectroscopy shows that the fluid compositions are mainly H2O, CO2, CH4 with a little CO2-3, indicating a reducing environment. TemperatureSalinity diagram of fluid inclusion data show three groupings. Zone “a” represents the originally high salinity exsolved fluid, zone “b” shows fluid immiscibility, and zone “c” shows the originally high salinity fluid mixed with lower salinity underground water. The fluid inclusions of each zone represent different evolutionary stages of primitive fluids which eventually formed the magmatic intrusion. The oreforming pressures calculated using fluid inclusions of type Ⅰ range from 860 MPa to 4158 MPa, and the pressures of A3 stage corrected using data from fluid inclusions of type Ⅱ and type Ⅳ range from 86 MPa to 115 MPa, while those in B1 stage range from 55 MPa to 93 MPa. The oreforming temperatures in A3 and B1 stages vary from 176℃ to 279℃ and 162℃ to 228℃, the oreforming depth varies from 362 km to 426 km. This study shows that high pressure occurred locally at the early period of fluid evolution, and fluid immiscibility may occur earlier than fluid mixing and further promoted fluid immiscibility. Changes of the fluid's physicalchemical conditions, fluid immiscibility and fluid mixing may be the leading factors of tungsten precipitation.