This article aimed to investigate the effectiveness of sodium silicate (water glass) in enhancing the engineering properties of low-expansivity soil. Improved soil samples were prepared by incorporating water glass at different mass ratios and curing them for varying periods. The swelling characteristics and shear strength of the treated soil were evaluated through free swell tests, zero-load swell tests, and direct shear tests. Additionally, X-ray diffraction and scanning electron microscope were employed to analyze the microstructural evolution and modification mechanism. The experimental results demonstrate that water glass effectively reduces the free swell ratio and zero-load swell ratio of low-expansivity soil. The optimal water glass content is found to be 4 %, with a 14-d curing period yielding the best performance. Furthermore, the shear strength of the improved soil increases with prolonged curing duration, showing a notable improvement in the internal friction angle. Microstructural analysis reveals that water glass enhances low-expansivity soil through two key mechanisms: altering hydrophilic clay minerals via ion exchange to reduce hydration shell thickness, and providing pore-filling and cementation effects from silica gels generated through sodium silicate hydrolysis.