The binary micrometer YSZ-TZP suspensions were prepared for the gel-casting molding of YSZ electrolyte in order to improve the mechanical properties of YSZ. The potential, sedimentation and viscosity of YSZ, TZP and TZP-YSZ suspensions were investigated. The results indicated that the dispersant (PAA NH4) can greatly affect the surface chemical properties of both YSZ and TZP, and it can also change the isoelectric points (IEP) of the two powders to lower pH value. The potential and sedimentation tests indicate that the stable suspensions are prepared when pH is between 8 and 10. The viscosity measurements showed that there exists an optimum dispersant content for each suspension. The lowest viscosity can be obtained at the optimum dispersant content. The solid content of the stable micrometer TZP-YSZ suspensions can reach as high as 50vol%.