Taking the Chang 6 tight sandstone reservoir in the Yan"an-Ganquan area in the southern Ordos Basin as an example, through casting thin sections, scanning electron microscope analysis, X-ray diffraction and high-pressure mercury intrusion experiments, combined with fractal theory, the fractal characteristics of the target reservoir were determined, and The relationship between fractal dimension and reservoir physical properties, pore characteristics and mineral composition is discussed. The research results show that the reservoir pores of the Chang 6 member in the study area are mainly intergranular pores and dissolution pores, which are ultra-low porosity and tight reservoirs; the fractal dimension of the reservoirs is generally greater than 2.5, the pore structure is complex, and the sorting property is poor. Strong homogeneity; the fractal dimension has a good correlation with the pore-throat characteristic parameters. The larger the fractal dimension, the uneven distribution of pores, poor connectivity, and weaker storage capacity and seepage capacity; the relationship between fractal dimension and mineral composition There is also a good correlation between them. Mineral composition and its content are the influencing factors that determine the complexity of pore throats, which in turn reflect the quality and pore structure characteristics of the reservoir.