This paper proposed a method for preparing subtle and complex lattice structure Al2O3 ceramic via digital light processing (DLP) 3D printing technology. The solid-phase mass fraction of Al2O3 ceramic slurry and the porosity of the green body reached 52% and 83%, respectively. According to the TG-DSC curve and two-way analysis of variance, the optimum technological parameters for debinding and sintering of Al2O3 ceramic green body were determined. The same shrinkage of Al2O3 ceramic prepared by pressureless sintering in all directions was confirmed. The density of sintered lattice structure Al2O3 ceramic was 95%, and the diameter of the lattice structure strut was about 170 mu m. XRD and Raman spectrum showed that the crystal phase of the sintered Al2O3 ceramic was alpha-phase, which has a good crystal quality. SEM results revealed a high density without significant pores and cracks sintered ceramic. The strict complex structure Al2O3 ceramic prepared by DLP technology had a compact microstructure and similar to the mechanical strength of Al2O3 prepared via the conventional shaping method, thereby providing an effective method for fabricating large specific surface area ceramic radiators and fine ceramic components in other fields.