The influencing factors on the reservoir development of Upper Taiyuan Formation in the eastern Ordos Basin were investigated. Experimental methods such as casting thin sections, high-pressure mercury intrusion, and constant-rate mercury intrusion were employed to examine the pore structure characteristics of Upper Taiyuan Formation, Tai 2 Member. Results show that the average porosity of Tai 2 Member reservoir is 7.84%, with an average permeability of 0.396 mD, primarily characterized by ultra-low porosity and permeability. The pore structure is complex, with strong heterogeneity. Various types of pores were developed in the reservoir, including intragranular dissolution pores, intergranular dissolution pores, intercrystalline pores, and rock fragment dissolution pores. Based on the frequency of pore development, porosity, and permeability in each region, the pore combinations are classified into three types: intragranular dissolution pores, intragranular dissolution pores combined with intercrystalline pores, and intragranular dissolution pores combined with intergranular dissolution pores. The experimental methods of high-pressure mercury intrusion and constant-rate mercury intrusion could effectively characterize the reservoir characteristics of these three types of pore combinations, among which the combination of intragranular dissolution pores and intercrystalline pores represents a favorable reservoir pore type. Based on the laws of sedimentary differentiation and pore differentiation, a set of criteria for evaluating high-quality reservoirs is established on the basis of experimental results. Upper Taiyuan Formation reservoir was classified into Class Ⅰ, Ⅱ, and Ⅲ from good to poor, and predictions were made for favorable areas of high-quality reservoirs.