In the process of direct acid leaching and de-alkali, the silicon in the red mud will also be partially leached, forming silica gel and other substances, which seriously affect the filtration performance of the red mud. In this paper, the calcium-containing substance CAM is added through the acid leaching process to capture the generated fine-grain silica gel and generate a precipitate, thereby improving the filtration performance of red mud acid leaching. Design two sets of test plans