The tight sandstone reservoir of Shanxi Formation in Yanchuan East Area of Yan'an Gas Field has complex petrological characteristics and heterogeneity. Clarifying its reservoir characteristics and favorable area distribution is of great significance for natural gas exploration and development. This article systematically studied the rock composition, pore structure, physical properties, and diagenetic evolution process of the Shanxi Formation reservoir through methods such as rock thin section identification, high-pressure mercury injection experiments, and physical property analysis. The results show that the Shanxi Formation reservoir is mainly composed of lithic quartz sandstone, with an average quartz content of 67.1%～71.8%. Residual intergranular pores, lithic dissolution pores, and microcracks are developed, and the pore throat structure is mainly micro throat type. The overall reservoir is characterized by ultra-low porosity and compactness. The reservoir performance of Shan 2 section is better than that of Shan 1 section, with an average porosity of 4.74% and an average permeability of 0.764 mD. The physical properties of the reservoir are controlled by particle size, plastic rock fragment content, and carbonate cementation, and the physical properties of coarse-grained sandstone and areas with low plastic rock fragment content are better. Based on sedimentary microfacies, sand body distribution, and structural characteristics, it is predicted that the favorable area of Shan 1 is located in the central southern part of the study area, while the favorable area of Shan 2 is distributed in a strip like pattern in the central and northern parts. This study provides geological basis for efficient exploration of tight gas reservoirs in the Shanxi Formation of the Ordos Basin.