The microstructure and pore characteristics of natural loess and CO2-silicification loess are qualitatively and quantitatively studied based on the test results from scanning electron microscope and digital image analysis and accelerated surface area-porosimetry system. The silicified loess samples have been curing for 13 years

19 years and 24 years respectively. It is found that the main structure type of CO2-silicification remains the same as that for the natural loess. the silicate gel and calcium(magnesium) silicate gel have only filled in the pores and adsorbed the surface of frame grains resulting in increase of contact area of frame particle. Being compared with natural loess

CO2-silicification loess isn’t reduced in pore size distribution and average pore diameter and area porosity and pore volume; the pore surface area of CO2-silicification loess has been increased from 17.8104 m2/g to 27.4735 m2/g. CO2-silicification loess mechanism is that the open structure in silicification loess remains

but a film of gels reinforces the bond strength of cement in microstructure and forms three dimensional networks of frame grains resulting in the collapsibility of silicification loess disappearing; and mechanical properties of silicification loess are improved.