Porous ceramics were fabricated from pressureless powder packing forming method using mullite and cordierite powders granulate by spray drying. The bending strength and shrinkage of porous ceramics were increased and their porosity were decreased with increasing temperature. It showed homogeneous distribution of 2$mu extrm{m}$ intergranular pores of mullite at 1400$^{circ}C$, 2.5$mu extrm{m}$ intergranular pores of cordierite at 1300$^{circ}C$ respedtively. Above that temperature intragranular particles were sintered and sintering by intergranular necking was extremely proceeded. In the test of thermal shock resistance sudden decrease of bending strength to $Delta$T was not shown because intergranular large pore prevented sudden crack propagation.