In order to systematically reveal the microscopic pore-throat structure and fractal feature of the seven sections of tight sandstone reservoirs in the Yanchang Formation within the Ansai Area of the Ordos Basin, by comprehensively wielding multiple technical means such as identification of casting thin section, surveys of scanning electron microscopy, testing of high-pressure mercury injection, and nuclear magnetic resonance experiments, combined with fractal theory, the intrinsic relationship among the fractal dimension of nuclear magnetic resonance and the physical property parameters of the reservoir voids, dynamic fluid saturation, and porosity was studied. An in-depth analysis was conducted on the pore throat structure parameters and the content of rock and mineral components. The research results show that the reservoirs in the study area have a typical nanoscale pore-throat system with strong pore-throat heterogeneity. Nuclear magnetic resonance (NMR) fractal analysis reveals that the reservoir exhibits pronounced two-stage fractal characteristics. The average fractal dimension of the pore throats for confined fluids is 1.56, indicating a relatively homogeneous distribution of pores and throats at the nanoscale. In contrast, the average fractal dimension of the pore throats for movable fluids reaches 2.99, suggesting a highly complex pore throat structure at the micrometer level. Expulsion pressure, the average radius of pore throat directly controls the reservoir seepage ability, quartz and feldspar content affect rock compressive properties and corrosion behavior. Clay minerals predominantly decrease the complexity of micropores, whereas interstitial materials alter the topological structure of the pore-throat system via filling processes. The nuclear magnetic resonance (NMR) fractal analysis method developed in this study has successfully provided a comprehensive description of the pore system in tight sandstone reservoirs, ranging from the nanometer to the micrometer scale. This method provides an important theoretical basis and strong technical support for reservoir quality assessment and optimization of development strategies.