Abstract: The adaptability of industrial ferro-nickle slag as road fill is studied using the laboratory and field tests. Firstly, chemical compositions of industrial ferro-nickel slag from various districts are tested and statistically analyzed to examine the main components and the relevant variability. The slag is then tested in laboratory to obtain particle characteristics (under different compaction efforts), shear strength index, CBR, percentage of powered slag in autoclave and resilient modulus, thus the mechanical behavior and index as road fills are evaluated. Based on this, full-scale field tests on ferro-nickel slag embankment are designed and implemented. The embankment settlement, deflection and pore water pressure are monitored during and after construction, and harmful substances are detected to assess their environmental impact. The study indicates that the ferro-nickel slags is largely composed of three components: SiO₂, MgO, and CaO. The MgO and CaO at free stage are expansive to some extent, therefore the soaked expansion of the slag shall be tested before adopted in roads. The ferro-nickel slag is defined as poorly graded gravel, with minor change of grading under standard compaction effort. The behavior of the slag as road fill can be improved by being mixed with clay of 10%~20% by mass. The field tests indicate that the ferro-nickel slag can be successfully applied in reinforced embankment. The monitoring settlement becomes stable at the initial stage of construction, and minor settlement occurs thereafter. The slag is highly premeable, thus the excess pore water pressure can be dissipiated immediately. According to the detected harmful substances, the ferro-nickel slag is a general industrial solid waste, which is conforming to the environmental requirements as road fills, and can be buried directly (no pre-processing required). According to the mechanical and environmental tests, the ferro-nickel slag is able to be adopted as road fills after appropriate improvement.