Abstract: The nano-silica was prepared by ammoniating process with sodium fluosilicate and with 3 different surfactants，i.e. cetyltrimethyl ammonium bromide（CTAB），tetrabutylammonium bromide（TBAB） or polyethylene glycol（PEG200），as template to change the morphology of crystals.The prepared sample was characterized by SEM，oil absorption value，and specific surface area analysis methods.It was observed that when using CTAB as template in the reaction，the performance of silica was the best.In addition，the effects of seed crystal，feeding rate of ammonia，and aging time on performance of nano-silica were investigated and the preparation conditions were also optimized.

Key words: sodium fluorosilicate, ammonolysis, surfactant, nano-silica