Mullite ceramics have recently been utilized as ceramic gas filters for high-temperature treatment of solid wastes due to their low thermal expansion coefficient and high refractoriness under load. In this experiment, mechanical, thermal and microstructural properties of porous mullite ceramics, which were used as carriers and high-temperature gas filters in food industry, were investigated as a function of starting raw materials. Porous mullite ceramics showed different microstructures depending on their starting materials. The specimen M2 had excellent resistance to thermal spalling and high mechanical strength. The average pore size varied from 0.3 ${mu}{ extrm}{m}$ to 16.6 ${mu}{ extrm}{m}$, and porous mullite ceramics fabricated by thermal decomposition of Al(OH)3 had very large pores and broad distribution of pore size.