The invention relates to a sizing agent for tape casting, which is prepared from zirconium dioxide powder, a dispersing agent, a low-boiling-point solvent, a high-boiling-point solvent, a binder and a plasticizer. By adopting a way of cooperating the high-boiling-point solvent and the low-boiling-point solvent, the low-boiling-point solvent can be preferentially eliminated during drying at a low-temperature section, while the high-boiling-point solvent is continuously and uniformly dispersed into a green body, the solvent evaporation speed in the sizing agent for tape casting is reduced, the phenomenon of surface crusting is avoided, and the high-boiling-point solvent can be uniformly eliminated during drying at a high-temperature section, so that a green body with uniform density is obtained. By cooperating with a dispersion method provided by the invention, the problem that the edge of the green body is warped is effectively solved, the granularity of the zirconium dioxide powder in the sizing agent is finer and smoother due to high-pressure dispersion, more uniformity in dispersion is realized, the adhesion between the sintered zirconium dioxide powder is more compact after sintering, and the compressive strength of the green body is improved.