Acid-leached waste residue, produced during Al extraction from coal ash, has been destroying the environment seriously. To utilize this high silicon residue (70% or more) and accelerate the industrialization of Al and Si extraction from coal ash, a high-silicon coal was selected to prepare catalytic gasification ash (CGA) and combustion ash (CA). Then, the obtained CGA and CA were leached by H2SO4 to remove aluminum and obtain silica-rich residue. After that, acid leached catalytic gasification residue (ACGR) and acid leached combustion residue (ACR) were leached by NaOH aqueous solution to extract SiO2. In this process, some possible influential factors such as NaOH concentration, liquid-solid ratio, reaction temperature and time on the extraction yield of SiO2 (EY-SiO2) and modulus of sodium silicate (SSM) were investigated respectively. Besides, orthogonal experiments L9(34) were conducted to analyze their interrelationship. In addition, to acquire the variation of crystal structure, the method of X-ra...