An Al2O3/5 vol.% mullite composite was synthesized by using reaction sintering of Al2O3/0.78 wt.% SiC at 1,600 degrees C for 2 h in air. The phase analysis of the Al2O3/mullite composite was carried out using X-ray diffraction (XRD). There were two kinds of mullite in alumina/mullite composite, namely, 3Al(2)O(3)center dot 2SiO(2) and Al5.65Si0.35O9.175. The microstructure of the Al2O3/mullite composite was investigated using scanning electron microscope (SEM) and transmission electron microscope (TEM). The mechanical properties such as Young's modulus, Poisson's ratio, hardness, toughness and strength of the Al2O3/mullite composite were investigated. The influence of mullite on the composite is discussed.