The BaiGan lake tungsten ore field is located in southeasten XINJIANG province，CHINA.It is a large deposit which was found in latest decade including Awar，Bashierxi，Baigan lake and Kekekaerd （marked KK for short）tungsten-tin deposit，among which the most explorered is the KK deposit.W-Sn Quartz veins are charactered by its echelon shape，Bending along strike and its low attitude. There are three stage of quartz veins，which can be interpretated as pre-mineralization quartz vein，ore-forming stage quartz vein and post-mineralization quartz vein,were defined at Kekekaerde（named KK shortly in this paper） W-Sn deposit. Fluid inclusions in the three stage quartz can be divided into five types: G-L two phases, G-L-D three phases,CO2 or water single phase,CO2-H2O three phases,and CO2-H2O-NaCl four phases. The first two are the main types in stage one quartz. Ore-forming satge quartz vein can be divided in two period and the first period was major W-Sn precipitating period and have all the five types of fluid inclusion. post-mineralization quartz contains mainly G-L two phases type. Ramman analysis results show that the liquid composition is H2O and CO2 while the gaseous composition contains minor CH4 and N2 as well. H-O isotopic composition of fluid inclusions in the three type veins indicate that ore-forming fluid is a mixture of magmatic water， atmospheric water and metamorphic water.Study on petrographic，microthermometry， and H-O isotopic analysis impy fluid immiscibility and fluid mixing，which may play a significant role for tungsten precipitation.