In foundation reinforcement, subgrade treatment, and anti-seepage wall construction, the mechanical properties of soil often do not meet project requirements. Cement-stabilized soil, known for its high strength, durability, and relatively simple construction process, is well-suited for a variety of soil types and complex geological conditions. To better understand the curing mechanism of fly ash cemented soil, this study examines the interaction between fly ash and cement paste. The effect of varying fly ash content on cement strength was investigated through unconfined compressive strength tests on hardened cement paste with different fly ash proportions. Additionally, the role of fly ash in the hydration process of cemented soil was analyzed using X-ray diffraction (XRD). The findings of this study provide valuable insights for applying fly ash in high-performance cement-based materials.