Abstract: The artificial seawater-mixed ternary composite grout composed of lead-zinc tailings, soda residue, and fly ash was developed to offer a new pathway for utilizing three solid wastes and conserving water resources. The hydraulic erosion resistance of solidified grouts with various mix proportions was investigated through strength, permeability, and drying shrinkage tests, and the evolution mechanisms of their macro performance were elucidated using SEM-EDS, TG-DSC, AFM, and MIP tests. The results indicate that artificial seawater, in conjunction with soda residue and fly ash, promotes the formation of hydration products, resulting in a denser and smoother surface morphology and a higher elastic modulus. These effects enhance pore filling and improve matrix compactness, leading to superior hydraulic erosion resistance in grouts with a high ratio of soda residue. In contrast, excessive lead-zinc tailings inhibit hydration reactions, reduce gel formation, and increase porosity, thereby weakening its macro performance development. The grout containing 48% soda residue and 40% lead-zinc tailings exhibits great water corrosion compressive strength (3.45 MPa) and low permeability coefficient (3.64×10^-7 cm/s under 1.5 MPa water pressure) after curing at 28 days, and its shrinkage ratio stabilizes at 0.014~0.047 during 4 to 25 drying days. After curing at 28 days, the chemical speciation of heavy metals in the grout gradually transforms into stable and inert forms, exhibiting low leaching toxicity and minimal environmental pollution risk. Overall, the new composite grout contributes to the comprehensive utilization of multiple solid wastes and demonstrates significant economic and environmental benefits.