Abstract: α-Al₂O₃ powders with D₅₀ of 0.171 μm and 0.432 μm were used as raw materials, the green bodies were prepared under various forming pressures and sintered at 1 450 ℃. The effects of particle size and forming pressure on the sintering behavior of α-Al₂O₃ powders were studied. α-Al₂O₃ powder with D₅₀ of 0.432 μm exhibited low sintering activity. The relative density of its green body increased from 54.1% to 56.6%, and the relative density of sintered body increased from 93.2% to 94.9%, when the forming pressure increased from 100 MPa to 300 MPa. α-Al₂O₃ powder with D₅₀ of 0.171μm exhibited high sintering activity, when the forming pressure increased from100 MPa to300 MPa. The relative density of its green body increased from 51.3% to 53.8%, but the relative density of sintered body maintained between 98.6%~98.8%. The results showed that improving the forming pressure had limited influence on sintering performance of α-Al₂O₃ powders. Reducing the particle size and improving the sintering activity was the key factors to increase sintering density and reduce sintering temperature of Al₂O₃ ceramic.