Microwave sintering method was carried out to prepare porous mullite composite. An insulation structure based on hybrid heating mode was well designed with the wall of mullite and the aided heaters of SiC. The obtained samples were characterized by XRD analysis, apparent porosity detection, and bending strength measurement. SEM was used to observe the microstructure of the sample. It is found that the porous mullite composite could be prepared through the microwave sintering within 2 h at relatively low temperatures around 1000 ℃. The lasted samples show comparatively superior properties to the products prepared by conventional processing.