Microscopic seepage characteristics are critical for the evaluation of tight sandstone reservoirs. In this study, a digital core approach integrating microscopic seepage simulation and CT scanning was developed to characterize microscopic seepage and fracture effectiveness (the ratio of micro-fractures that contributes to fluid flow) of tight sandstones. Numerical simulations were carried out for characterizations of tight sandstones. The results show that the axial permeability of the investigated cylindrical tight sandstone from Junggar Basin in China is 0.460 μm2, while the radial permeability is 0.3723 μm2, and the axial and radial effective fracture ratios are 0.4387 and 0.4806, respectively, indicating that cracks are not fully developed and the connectivity between micro-cracks is poor. Directional permeability that is difficult to measure by laboratory experiments can be obtained readily using the proposed method in this paper. The results provide important information for improving the exploration and development of tight sandstone reservoirs.