The effect of Al content and heating rate on the sintering behavior, microstructure, and mechanical properties of reaction bonded alumina (RBAO) was investigated. As the heating rate became slower a critical Al content which could be added to RBAO increased. The weight gain and linear shrinkage of RBAO containing of 55 vol% Al were 28% and 6.5%, respectively. The relative density of RBAO decreased from 96 to 94%, as the amount of Al increased from 15 to 55 vol%. The hardness of RBAO increased from 17.8 to 19.9 GPa and the bending strength enhanced from 370 to 570 MPa, as the amount of Al increased from 15 to 55 vol%. On the other hand, the wear rate of RBAO degraded from 6.7 to 3.39$ imes$10-5 $ extrm{mm}^2$/kg and the fracture toughness decreased from 4.1 to 3.6 MPa.m1/2, as the amount of Al increased from 15 to 55 vol%. Fracture modes were shown to the mixed mode of inter/transgranular. However, transgranular fracture was dominant with increasing the content of Al.