The efficiency of CMP is greatly dependent on the stability of slurry. The particles in stable slurry are well dispersed by overcoming attractive van der Waals forces. Polymeric surfactants such as poly(vinyl alcohol) and poly(acrylic acid) can be used as steric stabilizer. In this paper, the stability of silica slurry is investigated with rheological method. The effect of various volume fractions, and pH were investigated. PVA and PAA were chosen as polymeric stabilizer and the stabilizing effect of the amount added was studied. And the effect of molecular weight of PAA added was observed.