Abstract: The silica nanoparticles were prepared by air blowing method in a water-alcohol-ammonia solution with silicon tetrachloride，the by-product of polysilicon as the raw material，ammonia as neutralizer，and sodium dodecyl benzene sulfonate as modifier.The crystal structure，morphology，dispersion，and particle size of the product were characterized by Fourier transform infrared spectroscopy，X-ray diffraction，scanning electron microscopy，and transmission electron micoscope. The effects of ethanol/water ratios，ammonia dosage，dispersant species and dosage，H2O2 dosage，and other factors on the dispersion and particle size of silica nanoparticles were studied.The optimal synthesis conditions of silica nanoparticles were as follows: the total volume of mixed solution was 70 mL，the volume ratio of water/alcohol/ammonia was 38∶15∶12，the amount of SHMP was 1.5%（mass fraction），and H2O2 dosage was 5 mL.IR and XRD spectra demonstrated that the product was amorphous silica； TEM and SEM demonstrated that the silica nanoparticle size was about 100 nm and well-dispersed.

Key words: silicon tetrachloride, water-alcohol-ammonia solution, air blowing method, silica nanoparticles