In order to fabricate porous ceramics, hydrated sodium silicate was synthesized by hydrothermal reaction using anhydrous sodium silicate. The microstructural and the structural characteristics of the expanded ceramics were observed depending on heat treatment temperature (550, 600, 650, $700^{circ}C$) and then the effect of these characteristics on the compressive strength and the temperature gradient was investigated. As the heat treatment temperature was increased, the compressive strength was decreased from $0.717KN/cm^2;(550^{circ}C);to;0.166KN/cm^2;(700^{circ}C)$. The temperature gradient was increased with increasing the experimental temperature regardless of the heat treatment temperature. The temperature gradient of the expanded ceramics which was heat treated at $650^{circ}C;was;300^{circ}C$. The bulk specific gravity, porosity, pore size, pore characteristics and wall thickness were varied depending on heat treatment temperature, and the compressive strength and the temperature gradient were governed by the complex effects of these factors.