To examine the microstructure development in alumina ceramics, green bodies made by injection molding were densified under various conditions and examined by X-ray diffraction analysis and scanning electron microscopy coupled with image analysis. Although a previous paper showed that powder particles were oriented slightly, conventional characterization method used in the present study showed that the particles were randomly packed. Pronounced grain orientation occurred in the densification/grain growth process from the minor particle orientation in the green body. In the final ceramics, grains were aligned along the flow direction in the injection process.