Aiming at the remediation of Mu Us Sandy Land, which is one of the four major sandy areas in China, the local soft rock was selected as the remediation material for sand improvement, and the soil quality changes after the compounding of soft rock and sand were analyzed. The results show that the clay minerals in the soft rock are closely cemented to each other, forming a rich pore structure with a high hydrophilic, large specific surface and interlayer space. With the treatment of 1:1 and 1:2 soft rock/sand, there are more attachments on the surface of soil particles, and most of the particles are in contact with each other. The content of polysaccharides in the compound soil after the mixture of soft rock and sand is significantly higher than that of total sand treatment. With 1:1 of soft rock/sand, the content of free ferric oxide increased gradually with the depth of the soil layer. The organic carbon content in the 0–10 and 20–30 cm soil layers showed a good change. After the addition of arsenic sandstone, the soil cementation of compound soil and the content of polysaccharides and organic carbon have been significantly changed. Soft rock is a kind of natural material conducive to the improvement of sandy soil.