In order to prevent cracks, holes, warpage and other defects in sintered ceramic parts, ceramic paste with high solid content and low viscosity is needed based on light-curing 3D printing technology. By testing the flow and curing proformances, the selection and ratio of resin monomers were optimized. KH550, KH560 and KH570 were used to modify the surface of Al2O3 powder to improve flow performance and stability of ceramic paste. The mechanism of silane coupling agent reducing the viscosity of Al2O3 ceramic paste was discussed. Al2O3 ceramic paste with a solid content of 75% (mass fraction) (volume fraction of 45.5%) and a viscosity of 4 540 mPa·s was obtained. An optimization method for the preparation of light-curing Al2O3 ceramic paste was proposed, which is expected to be helpful for the preparation of 3D printing Al2O3 ceramic paste with high solid content and low viscosity for complex ceramics.