To study cementation force of compound soil mixed by soft rock and sand in Mu Us sand land in northern Shaanxi, we mix the soft rock and sand in different proportions to prepare compound soil, and then test the Raman spectra of the compound soil. According to the peak position of SiO2 at Raman shift 464 cm-1 varying with contents of the soft rock in the compound soil, we study the change of the cementation force of the compound soil particles. The results show that the peak position of the sand is 464.5 cm-1. With the increase of the content of the soft rock in the compound soil, the peak position decreases. This is because that the addition of the soft rock causes small particles in the soft rock to replace the position of large particles in the sand, the distance between soil particles increases, and the tensile stress appears due to tow between particles, which leads to the red shift of the Raman characteristic peak. When the volume ratio of soft rock to sand is 1∶1, the peak position decreases to 463.6 cm-1. When the volume ratio of soft rock to sand is 7∶5, the soil structure collapses and becomes firm, which results in the generation of compressive stress between particles. The compressive stress results in sudden increase of the peak position to 464.2 cm-1. Then the soil structure becomes stable. With the further increase of the soft rock content, there is still the replacement of samll particles of soft rock to large particles of sand, the tensile stress is obvious gradually, and the peak position constantly decreases to 463.1 cm-1 when the compound soil is sand. It is proved that the shifting of the peak position of SiO2 in Raman spectra can be applied to the study of cementation force between particles in compound soil.