The rheological behavior of sub-micron zinc oxide and alumina mixture powders aqueous suspension has been investigated over a wide range of volumetric solids loading (Ø = 0.2–0.55), in which polyacrylic acid (PAA) was used as a dispersant. The dependence of relative viscosity (ηr)–solids loading (Ø) determined experimentally was compared with models. The experimental results showed that the suspension apparent viscosity (η) reached a minimum as the dispersant addition reached 0.2 wt%, the viscosity increased with the solids loading and the rheological behavior of the suspension was content basically with the model proposed by Liu. From ηr–Ø relationship the maximum solid loading (Øm) was estimated to be 0.55, which was in accord with our experimental results.