For ceramic stereolithographic (SL) additive manufacturing, the solid loading of ceramic photosensitive slurry plays an important role during the SL process. In this study, Al₂O₃ ceramics were fabricated by SL additive manufacturing from photosensitive Al₂O₃ slurries with various solid loadings, and the solid loading-property relationships of Al₂O₃ ceramic were performed. The effects of solid loading on not only the rheological behavior and curing property of the photosensitive Al₂O₃ slurry but also the microstructure and mechanical properties of the Al₂O₃ ceramic were investigated. The results showed that both the viscosity and shear stress increased with the increase of the solid loading. High viscosity was greater than the critical value for self-leveling during the SL process. The curing properties of photosensitive Al₂O₃ slurries were highly depended on the sold loading. Moreover, clear effects on the defect characteristics of Al₂O₃ ceramics manufactured from various photosensitive slurries were observed. These manufactured defects are critical for the mechanical behavior of Al₂O₃ ceramic. In addition, the relationship between rheological behavior and curing property of photosensitive Al₂O₃ slurry. Meanwhile, the resulting microstructure and mechanical properties of the Al₂O₃ ceramic were also illustrated. Inhomogeneous structure caused by high viscosity can lead to a sintered ceramic with poor strength. These findings provide fundamental understanding for SL additive manufacturing of ceramics.