The properties of silica sol, such as the interface characteristics and microstr ucture, were comparatively studied by small angle x-ray scattering (SAXS) assis ted by dynamic light scattering. Four synthesis routes were adopted to relate th e properties of silica sol with the synthesis situation. Very big difference of SAXS results was found between the base-catalyzed and the acid-catalyzed silic a sols with ethanol used as solvent. Under the acid-catalysis of low molecule-w eight organic acid, not only were polysiloxane macromolecules obtained, particle suspension of silica was also produced with complicated inner structures of pa rticles. With ethanol or water as solvent, it was found that the silica particl e would become more irregular in morphology with more polarity of solvent. The formation of Si-O tetrahedron was more difficult in the acidolysis of tetraetho xysilane by formic acid than in the other hydrolysis routes. An interesting co- existing of positive deviation and negative deviation from Porod’s law was foun d in the silica sol with water solvent, and a detailed explanation has been giv en.Many nano-scaled structural difference among these different synthesis situa tions were revealed, which was difficult to be recognized by the experimental m ethods other than SAXS.