Abstract: Deep and ultra-deep oil and gas reservoirs buried at significant depths and subjected to ground stresses of 200 MPa, undergo notable changes in the pore microstructure of reservoir rocks. Digital core modeling serves as a crucial tool for pore-scale numerical simulations. However, current digital core reconstruction methods are based on scanning image reconstruction under normal temperature and pressure conditions and thus they fail to reflect the pore structure under high pressure conditions. Therefore, a digital core reconstruction method based on the discrete element method (DEM) was proposed by considering the effect of high stress. Initially, the watershed algorithm was employed to segment computed tomography (CT) images, and the contour database was established by the spherical harmonic analysis method. The Clump template library was established in PFC^3D. Then, according to porosity and particle size distribution, the Clump in template library was used to build a discrete element model. After, the accuracy of the model was evaluated via calculations of two-point correlation and linear path correlation function curves. Next, the micromechanical parameters between particles were calibrated, enabling simulation of the digital core under varying stress conditions. Finally, the pore geometry topology of the digital core under different stresses was analyzed, and porosity and permeability were calculated. Bentheim sandstone was taken as an example to construct digital cores under different stresses.. The research results show that high stress leads to reduced pore and throat radius, elongated throats, diminished connectivity, and lower porosity and permeability. The results provide technical support for pore-scale simulations of deep and ultra-deep oil and gas reservoirs..