The effects of dispersant ammonium poly(methacrylic acid) (PMAA-NH4) and poly(acrylic acid) (PAA) on nano-Al2O3 particle dispersion have been investigated. Under the same dispersion viscosity, Al2O3 of 38 nm size requires 20 times more PAA dispersant than Al2O3 of 0.2 mu m size but with only 9 times specific surface area increase. For the same carboxylic acid group to Al2O3 mole ratio, the PAA dispersant adsorbs more readily onto nano-Al2O3 particles than the PMAA-NH4 dispersant and has better dispersion efficiency. Rheology measurements confirm the better dispersion and higher dispersion efficiency when PAA is used. Maximum solids loading has been predicted for each suspension based on the rheological data; this predication capability can serve as the important guidance for future dispersion designs.