Abstract: Red mud is a kind of strong alkaline industrial solid waste produced in alumina production process. Traditional dam construction and storage will cause serious harm to the environment. In this paper, the red mud provided by a Bayer alumina plant in Shandong Province was taken as the research object, and a new process of fast, high efficiency and low cost decalcification of red mud was developed, which was dealkalized by sulfuric acid + calcium-containing compound salt CAM, and the soil transformation of decalcified red mud was studied. The results show that the sodium content in red mud can be reduced from 11.709% to 0.302%, and the alkali removal rate is as high as 97.42%. The red mud after alkali removal can be directly used in soil remediation, building materials, tailings filling and other industrial uses. The results of SEM analysis and pot experiment showed that the aggregate structure of red mud became larger from 1.25 μm to 17.5 μm and the soil properties were excellent after alkali removal, which could meet the growth requirements of tolerant plants. After reclamation, the structure of red mud mass becomes larger, which can accelerate the process of soil formation of red mud and provide technical support for in situ ecological restoration of red mud yard.