Thermodynamic stability,microvoid distribution and phases transformation of natural pozzolana opal shale (POS) were studied systematically in this work.XRD analysis showed that opal-CT,including microcrystal cristobalite and tridymite,is a major component of POS.DTA and FT-IR indicated that there were many hydroxyl groups and acid sites on the surface of amorphous SiO2 materials.FE-SEM analysis exhibited amorphous SiO2 particles (opal-A) covering over stacking sequences microcrystal cristobalite and tridymite.Meanwhile,MIP analysis demonstrated that porosity and pore size distribution of POS remained uniform below 600 ℃.Because stable porous microstructure is a key factor in improving photocatalyst activity,POS is suited to preparing highly active supported.