In order to study the effect of sodium silicate to improve the unfavorable engineering properties of expansive soil, this paper has studied the limits of water content, expansion, compaction, crack development and mechanical strength of the modified soil through laboratory tests. The results show that with the increase of sodium silicate content, the plastic limit of the modified soil is increased, the liquid limit is reduced, clay content and hydrophilic mineral decrease in soil; the maximum dry density of the modified soil decreases gradually, the optimal water content gradually increases, the compaction curve gradually becomes gentle; the expansion characteristics of the modified soil are obviously restrained and the strength is improved . It can be seen that the expansive soil modified by a certain content of sodium silicate can meet the engineering requirements.