In order to realize the green and low-carbon reuse of engineering muck, the effects of slag, fly ash and glass powder content on the mechanical properties of solidified soil at different ages (3,7,14,28 d) were studied. The microstructure and hydration products of solidified silt soil were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD), and the curing mechanism was revealed. The results show that the early strength of slag-fly ash and slag-glass powder composite solidified soil increases with the increase of slag content. When the proportion of slag is 50% to 60% (mass fraction), the early strength of slag-fly ash-glass powder ternary composite solidified soil can be effectively improved by increasing the content of glass powder. The error of unconfined compressive strength prediction model of solidified soil established by simplex centroid method is within 10%. Slag-glass powder composite solidified soil shows higher cohesion than slag-fly ash solidified soil at low slag content. The slag-fly ash-glass powder ternary composite curing system significantly improves the compactness of soil, and generates hydrated sodium aluminosilicate, hydrated calcium silicate and hydrated calcium aluminosilicate gel. These hydration products pack and bond the soil particles and improve the mechanical properties of solidified soil.