Clarifying the structural composition and mineral composition of arsenic sandstone is the basis for revealing the mechanism of soil erosion in the arsenic sandstone area and developing methods for controlling soil erosion in the arsenic sandstone area. This article analyzes the structural composition and mineral composition of arsenic sandstone in the Ordos area of Inner Mongolia by means of material analysis methods such as quantitative XRD and optical microscope analysis. The results show that：the structure of arsenic sandstone is composed of granular framework materials and clay-like cementing materials, and its cementing method is contact cementation; arsenic sandstone granular framework materials are mainly composed of quartz, calcium carbonate and feldspar, etc. Clay cementing materials are montmorillonite, chlorite, kaolinite and iron oxide, etc.; arsenic granular framework crystals (quartz and feldspar, etc.) rely on the cementing force of hydrophilic weak cementing clay materials. The solid mixture formed by friction between crystals, mechanical bite force and particle support is a ternary particle support permeable structure.