Abstract: Electrokinetic behavior of aqueous silicon nitride suspensions was studied by measuring zeta potential and effective particulate diameter.The isoelectric point of the silicon nitride powders was at the pH value of 4.2,and the parameters such as pH value and type of polyelectrolytes affected the surface charge and the stability of silicon nitride suspensions.A proper addition of anionic polyelectrolyte could lead to finely dispersed silicon nitride suspensions in the aqueous solution.