Abstract: Aiming at low-permeability sandstones, on the premise of reasonable preference of fracture criteria and based on the principle of geological mechanics, we established a mechanical model of the stress-strain field and parameters of fractures (aperture and density) by means of tests and theoretical derivation, and developed a set of quantitative methods using the relationship between fracture parameters and stress field. The results showed that the combination of an energy method with fracture criteria was an effective approach to establish the mechanical model of stress field and fracture parameters, when the inner stress state reached or exceeded failure conditions, the aperture and density of fractures would increase with the increase of strain energy density. At the same time, it was found that fractures in low-permeability sandstones formed commonly under paleo-stress field and their aperture and density were much larger than those under the current stress field. Consequently, it was concluded that the current stress field went against producing fractures and fracture aperture could be calculated through positive stress and shear stress acting on the fracture surface. Finally, a numerical simulation of current and paleo-stress fields and a prediction of fracture parameters were made on low-permeability sandstones from a reservoir of the middle third member of the Shahejie Formation in the Shinan oilfield and a good result was achieved.