The corundum-mullite bodies have high refractoriness under load and resistance to creep. Different  additives have been used in these bodies for improvement of sintering and microstructure. In this study, the effect of aluminium borate and magnesia additive on mechanical properties and sintering of alumina-mullite composite were investigated. Aluminum borate (9Al2O3.2B2O3) was prepared by the combustion of an aqueous solution containing stoichiometric amounts of aluminum nitrate, boric acid, and glycine. Tabular and gamma alumina, kaolin, and additives were mixed, pressed and then fired at 1400- 1500°C/3h for preparation of corundum-mullite samples. After firing the samples (without additives) at 1550°C/3h, bending strength (38 MPa), relative density (88%) with corundum and mullite as major phase and quartz as minor phase were obtained. After firing aluminium borate samples at 1550°C/3h due to high refractories of A9B2 the physical and mechanical properties weren't increased .With addition of 2.5wt% aluminium borate and 2.5wt% magnesia, after firing at 1550°C/3h, bending strength and relative density were improved and reach to 115Mpa and 95.5Mpa respectively. At this sample, corundum, mullite, pyrope (3MgO.Al2O3.3SiO2) and magnesia borate (2MgO.B2O3) were established at the sample