As an important optical material,transparent polycrystalline alumina (PCA) ceramic is widely used in aerospace,high-temperature windows,medical due to its high strength,corrosion resistance,high hardness,and excellent stability at high temperatures. Since Al₂O₃ belongs to the crystal structure of the trigonal crystal system ($a=b\ne c$),light is prone to birefringence when passing through the interior of the ceramic,and its transmittance is difficult to reach that of cubic crystal materials such as Y₂O₃ even under almost fully dense conditions. Using a special sintering process to decrease the sintering temperature and improve the real in-line transmittance of PCA ceramics has always been a research hotspot in related fields. In this work,a comprehensive review is made from the point of view of the sintering process based on the research status of transparent PCA ceramics in decades.