Mullite- zirconia composites have better mechanical properties than monolithic mullite ceramics and can be produced by reaction sintering of ZrSiO4 and -Al2O3. The samples were prepared from high-purity (99.9%) α-alumina and fine zircon (ZrO2>65 wt.%) powders using PVA as binder. The powder mixtures were compacted under 80 MPa as coin shaped samples by uniaxial dry pressing and then sintered in a multimode microwave field of 2.45 GHz. The microwave effect on ZrSiO4 dissociation and mullite formation was evaluated by comparing the microwave sintered samples with those sintered conventionally. The as-reacted compacts were characterized by X-ray diffraction and scanning electron microscopy (SEM). The effects of sintering parameters on mullitization and mullite grain growth were investigated.