One of the main reasons for the complex mineral composition，significant differences in lithology，and obvious differences in the production capacity of different gas wells after hydraulic fracturing in the Chang 8 reservoir in the Ordos Basin lies in the differences in the morphologies of the fracture networks formed by fracturing the reservoir rocks，which depends on the brittleness of the reservoir rocks. By taking Wuji，Ansai，and Shun 98 blocks in the Ordos Basin as the research object，representative rock samples were selected to carry out rock mechanics experiments，X-ray diffraction whole-rock mineral analysis experiments，and rock pore throat structure analysis. The dynamic and static mechanical parameters，mineral composition and content，and pore throat structure of the dense sandstone were obtained，and the dynamic brittleness index，static brittleness index，and mineral brittleness index of the rock were further calculated. The results show that the dynamic modulus of elasticity of rocks in the Chang 8 dense sandstone reservoir in the study area is larger than the static modulus of elasticity；the dynamic Poisson’s ratio is larger than the static Poisson’s ratio，and the dynamic and static mechanical parameters in the same block have a certain linear relationship.The transformation model of the dynamic and static mechanical parameters was established，featuring static brittleness index >dynamic brittleness index > mineral brittleness index for the same rock samples. Based on the graphs of each mineral content and the static brittleness index，it is clear that the brittle minerals in tight sandstone reservoirs in Wuji-Ansai block of the Ordos Basin are mainly quartz and carbonatite；there are differences in brittleness indexes among the blocks，featuring static brittleness index in Shun 98 block > static brittleness index in Ansai block > static brittleness index in Wuji block. According to the experimental results，the brittleness index is affected by the composition of rock minerals and the rock porosity，pore connectivity，and non-homogeneity. Under the premise of the same mineral composition，a weaker rock non-homogeneity means better pore connectivity and larger pore diameter，as well as greater brittleness.