Mullite ceramics have been known as the engineering materials due to their special properties such as high refractoriness, good thermal shock resistance, low thermal expansion, good strength at low and high temperatures, good creep resistance and low dielectric constant. In the present work, mullite samples were prepared by reaction sinteing of alumina and silica gel and subsequent sintering in a microwave process. The sintering of samples was carried out at temperatures in the range of 1400-1500°C with no soaking time. Density and porosity measurements showed a high density (89.3% TD) and low porosity (5.8%) for samples sintered at 1400°C under microwave conditions while for samples sintered conventionally at this temperature after 2h heating, density decreased (81.9% TD) and porosity increased (18.5%). By increasing sintering temperature to 1450 and 1500°C under microwave conditions, density increased (93.3 and 93.8% TD) and porosity decreased (0.31 and 0.36%), respectively. Microhardness measurements showed 27.6% increment when sintering temperature increased from 1400 to 1500°C. The mean grain size increased (34.8%) for samples sintered in furnace rather than those sintered in microwave process.