Abstract: The purity of sodium silicate solution is an important factor affecting the preparation of high purity silica by liquid phase method. The effects of Ca²⁺ on the impurity removal of sodium silicate solution, reaction time, reaction temperature and Ca-Si molar ratio were studied systematically. The removal rate of Al, Fe and Ti impurities in sodium silicate solution reached 95% after the reaction at 180 ℃ for 16 h with the addition of CaCl₂ at Ca-Si molar ratio of 1∶20. The crystal structure and surface morphology of the solids obtained from the impurity removal reaction were analyzed, which showed that impurity ions in the solution were removed by Ca²⁺ in the form of Ca-Si precipitate. Combined with the analysis results of the distribution of elements and the mass proportion of elements, it was proved that impurity ions were successfully combined into Ca-Si precipitate. Molecular simulation was used to explore the path of impurity removal reaction. The simulation results showed that Ca-Si precipitation was formed by the combination of Ca²⁺ and silicate formed by Si−O tetrahedron, in which Si in some Si−O tetrahedron was replaced by Al, Fe, Ti and other metal impurity ions, forming Ca precipitates containing metal impurities. Therefore, Al, Fe, Ti and other elements appear in the precipitation, and ions such as Na and K enter the precipitation due to charge attraction, forming various silicate precipitates. With the change of crystal cell volume as the criterion for the formation of impurity ions, the increase of lattice energy proves that the impurity removal reaction generates stable precipitation, which provides theoretical guidance for the mechanism of Ca²⁺ formation of silicate precipitation and absorption of impurities in sodium silicate solution.