Miscellaneous fill, steel slag, and slag powder were mixed to prepare steel slag-miscellaneous fill base material by soil solidification technology. On this basis, the effect of main materials including steel slag, concrete crushed material and plain soil on the strength of base materials were conducted, regression model was established to obtain optimal mixing ratio of the main materials steel slag of 51.98%, concrete crushing material of 28.44%, Plain soil of 19.57%. Verification test on the optimized mix ratio was carried out. The base materials with optimized mix ratio presented the 7d unconfined compressive strength of 11.55MPa, the 28d indirect tensile strength of 2.026MPa with error less than 2% compared with regression model prediction value. The orthogonal test was further applied to the experimental research on the mixture ratio of each admixture. It was confirmed that orthogonal test results was basically consistent with main material coupling influence test.The optimal mix ratio was as follows: 50% steel slag, 50% miscellaneous fill (concrete crushing material: plain soil = 6:4), 5% cement, 40% of slag powder, 0.02% soil curing agent. It presented 7d unconfined compressive strength of 11.93MPa with 28d indirect tensile strength of 2.050MPa. The steel slag-miscellaneous fill specimens with the optimal mix ratio exhibited significantly enhanced strength with the increase of age, and the unconfined compressive strength of the sample at 90 days was 2.27 times compared with that at 7 days, the expansion rate with 30-day high temperature water bath was only1.03%.X-ray diffraction analysis (XRD) and electron microscope scanning (SEM) test results showed that: SiO2 in slag powder reacted with f-CaO in steel slag to form a hydrated calcium silicate gel (C-S-H) and the modification effect of the soil solidification agent on the soil were the key to solving the expansion of steel slag. Concrete crushing material and steel slag could support steel slag-miscellaneous fill structure, CSH gel gradually generated with the increase of age, forming a coral-like and flaky structure, which could enhance compactness of the steel slag-miscellaneous fill base material, resulting in continuous increase of strength for base material.