Aiming at the problems such as insufficient early strength of cement-stabilized soil and high energy consumption, high pollution and high cost in the preparation process. In this study, sodium silicate was used to excite the substrate polymer of slag-fly ash for soil solidification. Firstly, the optimal alkali equivalent under different slag-fly ash ratios was determined through direct shear tests. On this basis, the effects of slag-fly ash ratios, curing age and dosage on shear strength were explored. Meanwhile, the curing mechanism was revealed by combining electron microscopy scanning (SEM) and X-ray energy dispersive spectroscopy (EDS) experiments, and was compared with that of cement-cured soil. The results show that with the increase of curing age and the dosage of curing agent, it is conducive to the improvement of the shear strength, internal friction Angle and cohesion of the cured soil. With the increase of the proportion of fly ash, the shear strength, internal friction Angle and cohesion of the solidified soil gradually decrease. Compared with cement-solidified soil, the base polymer of slag - fly ash can effectively enhance the shear strength of solidified soil. The cementitious products such as calcium silicate hydrate (C-S-H) and calcium aluminate hydrate (C-A-H) generated by it can effectively bond soil particles and fill soil gaps, which is the main reason for the improvement of the shear strength of solidified soil.