The seismogenic fault of the Mw 7.9 Wenchuan earthquake showed a high-angle reverse slip,and the high pore fluid pressure mightly exist in the deep fault,which is favorable for the sliding of the fault.The current technologies can not give us the fluid status of the fault in the middle crust.We estimated the fluid status of the deep fault in early geological history by studying the deformed granites uplifted to the surface,which could help to reconstruct the rheological structure to understand the mechanism of the large earthquakes occurrence in the Longmenshan region,such as the Mw 7.9 Wenchuan earthquake.Deformed granites were collected in a ductile shear zone found in the southern section of the Yingxiu-Beichuan fault.The microstructures showed that inhomogeneous ductile deformation occurred in the deep of the Yingxiu-Beichuan fault.The quartz and feldspar in the ductile shear zone were deformed by the subgrain rotation recrystallization,indicating the deformation temperature ranges from 400 to 500 oC and the flow stress ranges from 15 to 80 Mpa.Using micro-thermometer and Laser Raman microspectrometer,we measured the fluid compositions,ice melting temperature and homogenization temperature in fluid inclusions with the composition of NaCl-H2O,and the temperature of fluid capture is estimated from 330 to 350 oC,corresponding to the depth is 18-19 km in the Longmengshan fault,which indicates the fluid pressure coefficient from 0.2 to 0.85,implying sublithostatic pore fluid pressure existed locally.High pore fluid pressure could weaken the fault significantly and increase the depth of the brittle-plastic transition zone according to the rheological structure of the Longmenshan region which considering the pore fluid pressure.All of these could help to trigger the brittle fault slip on the top of the brittle-plastic transition zone.