Abstract: The present article studied the hot pressing technology of B₄C and the influence of Al₂O₃ on the sintering properties of hot pressed B₄C. It was found that densified sintering product of about 1.0μm B₄C and with addition Al₂O₃ as sintering assistant could be obtained by hot pressing at 1750℃ and 35MPa while hot pressing at over 2100℃ is needed to densify the materials of pure B₄C materials.5%~30% addition of Al₂O₃ can obviously decrease hot pressing temperature of B₄C materials. But such role will not be distinct with the increase of Al₂O₃ contents which will on the contrary decrease the hardness of the materials. In case of Al₂O₃ contents of 5%~10% (wt) the hardness of materials equal HRA 96.5 which is comparatively approximate to the hot pressed pure B₄C materials of HRA 97.0.