Abstract: Start with west Sichuang Dayi structure,current structure train characteristic,use finite element numerical analysis technology,simulate study area Xu 3 member gas reservoir rock body paleo-tectonic stress fields and fracturing proximity coefficient(η),compare η with real data and field observation,determine various fracture development degree and its related η,combine rock mechanics,structural geological theory,field fracture observation and real production data,predict Dayi structural Xu 3 member fracture development degree,types and shapes.The result indicates that fracture in Dayi tectonic Xu 3 member is better developed,fracture distributed regularly,mainly near the Dayi tectonic fault,the fault overlapping spot,the fault end,tectonic high steep belt,fracture growth position is the north west to and north east,the main fracture type is high angle shear fracture,low angle shear fracture and extension fracture.