Abstract: Solidification is one of the chemical methods for collapsible loess treatment. For better solidification effect, sodium silicate is modified by various methods. The mechanical strength of loess reinforced with compound modification sodium silicate is studied in this paper. The physical components such as chemical composition and mineral composition, microstructure are tested and analyzed by carrying out X-ray diffraction, scanning electron microscope and mercury porosimeter. The results show that the mechanical strength of reinforced loess is significantly improved. Diffraction intensity of parts of the mineral is increasing in the X-ray diffraction patterns. Low density amorphous phase peak groups still exists. The SEM images show that crack of gel films is reduced, and bonding relatively is tended to close. Surface area of pores is increased and mode pore diameters are reduced after sodium silicate is modified. The mechanism of loess reinforced with the compound modification sodium silicate is due to reinforcement of the bond strength of cement in microstructure and formation of three dimensional networks of frame.