Abstract: A solidification/stabilization approach was employed to modify riverbed silt， synthesizing it into road subbase material. The macroscopic properties and microscopic structural changes of the material were comprehensively analyzed through unconfined compressive strength tests， mineral structure composition analysis， pore structure tests and X‑ray photoelectron spectroscopy. The experimental results indicated that the material achieved an unconfined compressive strength of 4.0 MPa at 28 d. The optimal mass fraction of the binder was found to be 63% slag， 21% fly ash， 14% activator and 2% activator. The mineral composition was dominated by quartz and clinoptilolite， while the pore structure conforms to type Ⅳ isotherms， H₃ hysteresis loop， with a maximum adsorption capacity of 40.52 cm³/g. Additionally， the material generated substances such as SiO₂（Al₂O₃）_2.1， SiO₂（Al₂O₃）_0.55， CaSiO₃ and CaCO₃， contributing to the enhancement of strength. The results showed that modification and activation can effectively enhance the chemical activity of sediment absorption at the bottom of the river， meeting the minimum strength limit requirements of road subbase materials in the “Construction and Quality Acceptance Specification for Urban Road Engineering （CJJ1—2008）”， and can be used as road subbase filler.