Silicon slag is a kind of solid waste produced in the reaction between fluorosilicate and aluminum hydroxide when aluminum fluoride is produced by fluorosilicate method. Aluminum fluoride is mainly used as auxiliary solvent in electrolytic aluminum industry in China and the demand is huge. Therefore, a large number of silicon slag wastes are produced. Enterprises usually store silicon slag by stockpiling, resulting in large land occupation and environmental pollution. Silicon slag contains valuable elements which can be reused is a protection of resources. In this work, a silicon residue in Yunnan Province is used as the research object. The silicon residue is acidified by concentrated sulfuric acid and the leaching rate is calculated according to the residual amount of aluminum and fluorine after acidification. A single-factor experimental scheme for the acidification process of silicon slag is designed by studying the effects of acid dosage, reaction temperature and reaction time in the acidification process of silicon slag. The phases of silicon slag, acid slag and final product are analyzed by XRD. The results show that when concentrated sulfuric acid with 1.3 times the amount of theoretical acid (23.66 g) is added, the reaction temperature is 170℃ and the reaction time is 90 min, the leaching rate of aluminum is greater than 99%, the leaching rate of fluorine is greater than 97%, and the purity of SiO2 is rapidly increased to more than 99.00%. The acidification process of silicon slag is studied by kinetic experiments. The results show that the acidification process of silicon slag conformed to the shrinking unreacted core model in the liquid-solid multiphase reaction. The activation energy of the reaction is 62.97 kJ/mol and the leaching process is controlled by chemical reactions. The proposed method provides a new idea for the utilization of silicon slag, which has the advantages of short reaction time, less water consumption and high leaching rate of valuable elements after acidification.