Abstract: AlON transparent ceramic is a new structure-function integration optical material with excellent optical, thermal, and mechanical properties, which can be widely used in missile domes, and transparent armors and other fields. The preparation of green body with high density and homogeneous microstructure is the key technical procedure for fabricating AlON transparent ceramic. However, nanopowders possess high specific surface area and are easy to form non-uniform agglomeration, resulting in poor density of formed green body. In order to improve density and homogeneity of green body, micro-spheroidization of nanopowders and dense spherical particles with a diameter greater than 10 μm and good fluidity were obtained by optimizing the spray granulation process. The effect of cold isostatic pressing pressure on density, microstructure, average pore diameter of green bodies, and optical transmittance of sintered ceramics were intensively investigated. Green bodies with relative density of 58.8% were obtained. The in-line transmittance of sintered ceramics reached 83% at 2000 nm (thickness 2 mm). AlON transparent ceramics with diameter of Φ170 mm plate and Φ110 mm dome were obtained by cold isostatic pressing and pressureless sintering.