Abstract: To address the insufficient early strength of cement-solidified soft soil, along with the high pollution and energy consumption associated with cement production, a blend of slag-based geopolymer and cement is utilized as the binding agent for solidifying marine soft clay. A series of unconfined compression strength tests, scanning electron microscope analyses, and X-ray diffraction tests are conducted to examine the impacts of slag and sodium silicate on the mechanical characteristics of high-water-content soft clay. The results demonstrate that the addition of slag to cement notably boosts the soil strength, an effect that becomes more pronounced with higher replacement proportions and sodium silicate concentrations. The microstructural analysis reveals that the slag-based geopolymer acts as an intergranular pore filler, enhancing compactness and refining particle structural alignment by facilitating the formation of hydration cementation products, thereby enhancing soil integrity. This enhancement is evident through a macroscopic increase in the compressive strength of the solidified soil. These findings provide theoretical insights for employing the conventional cement mixing pile reinforcement techniques in soft soil applications.