The highly porous cordierite ceramics were fabricated combining the merits of direct foaming and gelcasting method. The content of gum arabic had a great influence on the foaming capacity and the stability of the wet slurry foam. And the foaming capacity mainly affected the porosity while the stability mainly affected the pore size. The highest porosity of 90% was obtained at 0.4 wt.% gum arabic content and the smallest pore size and the most homogeneous pore distribution were arrived at 1.2 wt.% gum arabic content. As the sintering temperature increased, the porosity and pore size decreased but the uniformity of the pore distribution increased. Moreover, the thermal conductivity was mainly affected not only by the porosity, but also by the sintering degree of the cordierite substrate.