Abstract: Porous diatomite ceramics were prepared by foam-gelcasting method after holding at 1 000℃ for 2 h with industrial diatomite fine powder as raw material and sodium silicate as sintering aid. The addition amount (0-5wt%) of sodium silicate on the phase composition, microstructure, pore size and compressive strength of the ceramics were investigated. The results show that with increasing addition amount of sodium silicate, the cristobalite content decreased while the tridymite content increased in the porous diatomite ceramics, the sintering densification increased, the pore size showed a decreasing trend, and the compressive strength was improved. When the addition amount of sodium silicate was 3wt%, the diatomite ceramics with a hierarchically pore-structure were obtained; the compressive strength was (1.13±0.08) MPa, which increased by about 113% comparing with that without sodium silicate, and the thermal conductivity at 200℃ was (0.098±0.002) W·m^-1·K^-1.