Aqueous Y2O3 suspension was prepared by Y2O3 nano powders with a specific surface area of 18.1 m2/g as raw material and ammonium citrate (TAC) as dispersant, respectively. The influence of concentration of TAC, pH value, ball-milling time and solid loading on the rheological behavior of Y2O3 suspension was investigated. The results indicate that the stable and well-dispersed suspension with 2.2%(mass fraction) TAC and pH value in the range of 9.4 to 11.5 was achieved after 8 h ball-milling. The viscosity of the suspensions increases with increasing solid loading, and the green body of slip casting from 33%(volume fraction) suspension has the highest density. Compared with the traditional die pressing, more homogeneous powder particles in green bodies by slip casting are obtained.