Abstract: Sodium silicate nanahydrate and PAM were selected as dispersants to evaluate the dispersive stability of nanoparticles through a diffraction-based laser granulometric analyzer. An IR spectrometer was used to identify the adsorption state of dispersant in the surface of nanoparticles. The results indicated that the combination of sodium silicate nanahydrate with PAM can play the role of synergistic reaction to improve effectively the dispersive stability of SiO2 nanoparticles in aqueous solution. It was found that adding the sodium silicate nanahydrate before PAM is better than adding them in reverse order for dispersive stability, if the amounts of both additions are the same.