Fluid solidified soil is a new material developed in recent years to improve backfill quality of narrow space in municipal and construction engineering. In this paper, steel slag powder, CFB desulfurization ash, rice husk ash and other low-quality solid wastes were used as clinker-free cementitious materials to prepare fluid solidified soil, and the unconfined compressive strength, drying shrinkage property, heavy metal leaching property and microstructure of fluid solidified soil were tested. The research shows that the flow expansion degree and unconfined compressive strength of fluid solidified soil prepared by cementitious materials without clinker meet the requirements of general filling engineering, the drying shrinkage value of hardened body is significantly lower than that of cement solidified soil with the same content, and there is no risk of excessive leaching toxicity of heavy metals. Under the synergistic effect of various solid wastes, the soil particles aggregate into clusters, and the pores are significantly reduced. The flocculent gel and acicular ettringite crystal are intertwined, adhere to the surface of soil particles and connect to soil particles, which enhance the strength of solidified soil.