Extrusion freeforming (EFF)-based 3D printing of ceramic materials is an additive manufacturing technology that builds 3D objects through layer-wise slurry deposition (LSP) of ceramics. This process offers advantages such as a high efficiency of formation, wide applicability, and low cost. The effect of solids content on the rheological behavior of Al₂O₃ ceramic slurry, and the effect of sintering temperature on microscopic morphologies and the precision of the parts fabricated by 3D printing, were investigated. Results show that the slurry viscosity gradually increases while the slurry flowability is reduced with an increasing solids content. Solids content should be high enough to prepare highly compact ceramic parts, however, an over-high solids content is likely to decrease the flowability of ceramic slurry. The optimal solids content was determined to be 50 vol%. As the sintering temperature increases, the green bodies become more compact and develop fewer cracks. However, the ceramic particles will be transformed to liquid phase at a high sintering temperature, which affects the shapes of sintered samples. The optimal sintering temperature was determined to be 1700°C. After being sintered at high temperature, the samples are found to be free from obvious surface defects or deformations and show slight uniform shrinkage, with a shrinkage rate of 20%. Surface roughness also decreases indicating that surface quality has improved. Finally, a set of sample ceramic structures were printed using optimized process parameters.