In view of the high water content of desulfurized ash buried at the bottom of the lake and the poor feasibility of reuse after dehydration and drying, in this study, the natural properties of semi-dry desulfurized ash paste were directly used to prepare full-solid waste fluid filling material. The "semi-dry desulfurization ash, steel slag powder and fly ash" full-solid waste cementification material was studied. The effect of raw material ratio on compressive strength was investigated. The gelling mechanism was studied by means of XRD, FT-IR, SEM and other analysis methods, and the influencing factors on the strength of fluid filling material were investigated. The results show that, the optimal ratio of raw materials is desulfurization ash: fly ash: steel slag powder = 40: 20: 40, and the compressive strength of 28 d can reach 13.37 MPa. In addition to the conventional C—S—H gel and ettringite, there is also a small amount of hexagonal-shaped crystal C₃A—CaSO₄—11H₂O, which are generated by the reaction of CaSO₄·0.5H₂O in desulfurization ash and C—A—H in the system. When the ratio of curing agent is in the range of 8%~20%, the 28 d compressive strength of the prepared fluid fill is 1.18 ~ 2.47 MPa. Triethanolamine can improve the compressive strength of the fluid filling at different ages. The best results can be obtained when the dosage is 0.04% of the curing agent mass. When the dosage of curing agent is 8%, the main index of the prepared fluid material meets the standard requirements and the feasibility is good.