Abstract: Gonggashan granite is a syntectonic granite, emplaced at 12.8±1.4 Ma. It extends parallel to Xianshuihe fault, which is a major active sinistral strike-slip fault in eastern Tibet Plateau. Along Chuanzang Road cross section and Maoniugou to Tagong Grassland cross section, 10 oriented specimen were collected to conduct the fluid inclusion planes (FIP) study. The attitudes of FIP measured on Fedoroff universal stage show that the preferred orientation is EW and subvertical. The FIP results indicate that the Gonggashan granite suffered E-W horizontal compression，which is consistent with the sinistral slip of Xianshuihe fault. Laser Raman Microspectroscopy data reveal that most of fluid inclusions in FIP are of NaCl-H2O composition. Microthermometric analysis of fluid inclusions allows distingction of two general types: Type A is characterized by Tm ice in the range of －9.0 to －8.2℃ (salinity 11.9%~12.8%) , Th varies from 126.0 up to 197.0℃ . Type B is characterized by Tm ice in the range of －4.7 to －0.5℃ (salinity 0.9%~7.4%) , Th varies from 144.0 up to 314.6℃. The FIP of Gonggashan granite reveals two stages of fluid percolation，and both evolved with declined temperature and salinity. Paying more attention to syntectonic Gonggashan granitic magmatism and its relationship with Xianshuihe faults is of very important scientific significance in understanding the deformation mechanism of Tibet Plateau.