Abstract: Tight sandstone reservoirs of the Lower Shihezi Formation in the Ordos Basin are characterized by poor physical properties, abnormal formation pressure, and the development of high-strength interlayers, etc. Thus, the selection of mechanical parameters and the fracturing characteristics of the reservoirs are significant for the effective development of oil and gas fields. For the tight sandstone samples from the Lower Shihezi Formation in the Hangjinqi area of the Ordos Basin, we carried out parallel experiments to test tensile strength, and to make triaxial mechanical experiments with high temperature and high pressure of in-situ conditions. Based on granularity classification, the mechanical strength properties and fracturing characteristics of tight sandstones were discussed. The tight sandstones in the Lower Shihezi Formation can be classified as medium- to fine-grained lithic sandstones, coarse-grained lithic sandstones, and giant- to coarse-grained lithic sandstones. The coarser the particle size, the better the physical properties, and the higher the quartz content, the lower the clay content. As particle size increases from fine to coarse, the mechanical strength and elastic parameters gradually decrease, and the ability of rock to resist deformation and maintain structural integrity decreases. The fracturing of the samples show the characteristics of brittleness to matrix mixing. Under the same stress and construction conditions, different rock types will result in various reservoir fracturing difficulty and stimulation effects. Different engineering mechanic parameters should be selected according to actual formation conditions.