Geopolymer is a new type of silica-aluminium material with amorphous three-dimensional network structure, which is obtained by appropriate process and chemical reaction with SiO₂ and Al₂O₃ as main components. Using geopolymers to partially replace cement for soil solidification not only reduces the amount of cement, but also improves the strength and durability of solidified soil. In this study, fly ash-based geopolymer was used to partially replace cement to solidify powdery soil. The effects of different curing agent ratios, proportion of fly ash-based geopolymer replacing cement, water content, and curing time on the unconfined compressive strength of solidified soil were investigated. The results show that the curing effect of fly ash-based geopolymer partially replacing cement on soil is significantly improved. When the curing agent content is 8%~15% (mass fraction), the unconfined compressive strength of the solidified soil is greater, and the strength growth rate is faster. With the increase of the proportion of fly ash-based geopolymer replacing cement, the unconfined compressive strength of solidified soil increases first and then decreases. When the water content is 28%, the proportion of fly ash-based geopolymer is 5% (mass fraction), and the curing time is 60 d, the unconfined compressive strength of solidified soil reaches the maximum value. When the proportion of fly ash-based geopolymer is 10% and 15% (mass fraction), the unconfined compressive strength of solidified soil increases first and then decreases with the increase of water content. When the proportion of fly ash-based geopolymer is 0% and 5% (mass fraction), the unconfined compressive strength of solidified soil decreases with the increase of fly ash-based water content. With the increase of fly ash-based geopolymer content, the stress-strain curve slope of solidified soil first increases and then decreases.