Abstract: Using crystal waste of industrial production as raw material,after pretreatment with hydrochloric acid,the raw material was dissolved in the mixture solution of sulfuric acid and hydrogen peroxide to extract silica from it.Firstly,influence of single factors,such as concentration of sulfuric acid,dosage of hydrogen peroxide,reaction time,and reaction&nbsp; tempe-rature,on the purity of silica were studied,and a better factor level was confirmed.L<SUB>8</SUB> (4×2<SUP>4</SUP>) orthogonal layout was adopted in orthogonal experiments and effects of concentration of sulfuric acid,dosage of hydrogen peroxide,reaction time,and reaction temperature on purity of silica were investigated.Result indicated that purity of silica decreased with the increasing of concentration of sulfuric acid,greatly increased with the increasing of dosage of hydrogen peroxide and slightly increased with the increasing of reaction time and temperature.Through orthogonal experiment the optimal process parameters were obtained,which were: concentration of sulfuric acid is 0.5 mol/L,hydrogen peroxide′s volume is 15 mL,water bath temperature is 343 K,and reaction time is 120 min.Under these conditions purity of silica could reach 99% above.