A new method is used to quantify the relationships between stress field and primary fracture characters(aperture,density)in low-permeability sandstone reservoirs based on laboratory experiments and mathematical development,through which,quantitative fracture modeling is set up.Using this modeling,we can load it into the stress analysis software(Ansys 10.0)to acquire 3D palaeostress field and current-stress field after selecting appropriate mechanical parameters and stress loading.