Abstract: Taking a domestic vein quartz ore as raw material，aiming at the purity requirement of high purity quartz sand（4N8 grade，SiO2 content≥99.998%）for the inner sand of quartz crucible，a "surface-in‐ side" echelon impurity removal process route was proposed. Through the synergistic purification of crushing and screening-one-step acid leaching-roasting water quenching-two-step acid leaching-chlorination roast‐ ing-water leaching process，the removal effect of step-by-step acid leaching on different forms of impuri‐ ties was systematically explored. The results showed that one-step acid leaching（hydrochloric acid + sulfu‐ ric acid + hydrofluoric acid mixed acid）can effectively remove surface free impurities and mineral structure impurities，and increase the purity of quartz sand to 99.97%. Roasting water quenching（1 150 °C）com‐ bined with two-step acid leaching significantly reduced the content of fluid inclusions and lattice impuri‐ ties，and the total content of impurities decreased to 53.19 μg/g. Finally，the alkali earth metals & alkaline earth metals were converted into volatile or soluble chlorides by chlorination roasting（1 200 °C）. The total impurity content was further reduced to 15.87 μg/g，and the purity of SiO2 reached 99.998 4%. The 13 impu‐ rity elements of the product fully meet the requirements of GB/ T 45823-2025，and meet the standard of American silicon-based photovoltaic grade product（IOTA-CG）. The research results provide a reliable technical path for the large-scale preparation of 4N8 high-purity quartz sand by domestic vein quartz ore， which is of great significance to break through the international monopoly and ensure the supply of key raw materials in the photovoltaic industry.

Key words: high purity quartz sand, vein quartz ore, echelon impurity, acid leaching, chlorination roasting, 4N8 grade