Abstract: Using the oil shale ash in Maoming，Guangdong as the raw material，nano-silica was prepared by acid leaching process.The effect of parameters of alkaline leaching process on yield of silica was particularly studied，and the optimum conditions were obtained:concentration of NaOH was 3 mol/L，amount-of-substance ratio of NaOH to SiO2 was 4∶1，leaching time was 4 h，and leaching temperature was 90 ℃.Under the optimal conditions，the yield of silica was 63.79% and the size of silica was 54 nm.The quality of prepared product could meet the requirement of the standard of HG/T 3061—1999.

Key words: oil shale ash, nano-sized silica, acidic method, alkaline leaching, yield