Hydrothermal solidification/synthesis of diatomaceous earth based material has been carried out so as to investigate the relationship between porous and mechanical properties. Compaction pressure could make contact of particles closer, which accelerated the hydrothermal reaction and thus improved the strength of the solidified specimen; however, it could shrink the pore volume yet seemed to exert a small influence on the surface area. Curing time and temperature affected the porous and mechanical properties of synthesized specimens significantly, and the toughest specimen seemed to possess the largest surface area and optimum pore size distribution. As such, a porous and tough humidity regulating material seemed to be manufactured easily by the hydrothermal solidification/synthesis technology.