The effect of particle size, pH value and dispersant on the rheological properties, Zeta potential, viscosity and stability of slurry and its mechanism were studied. The experimental results show that the viscosity of slurry increases and the stability increases with the decrease of particle size at the same shear rate. When no dispersant is added in the slurry, the absolute value of Zeta potential of the ultra-fine magnesium aluminate spinel slurry under acidic condition is higher than that in alkaline condition. While, in the presence of dispersant, the pH value corresponding to the isoelectric point moves in an acidic direction, and the percentage of dispersant required for preparing low viscosity slurry decreases with the increase of solid content. pH value and dispersant content have the best range, if too high or too low, the rheological and stability of the slurry will be worse. The absolute value of the Zeta potential is just one aspect that affects the stability of the slurry, and if the dispersant is excessively large, even if the slurry particles Zeta potential absolute value is large, and the slurry will produce agglomeration and flocculation.