Electrical Furnace Steel slag (EAF) was converted into steel slag nanocomposite (SSNC) by solvothermal preparation technique and assisted by H2O2 for Fenton and photo-Fenton-like degradation of six different dyes in both suspension and spin-coated modes. The physico-chemical properties were evaluated using various characterization tools. The result reveals that the EAF-SSNC exhibited nanocomposite behaviour. As a substrate for studying the advance oxidataion processes, methylene blue (MB) was first used. The kinetic study followed the pseudo-first-order reaction kinetics. The effect of operating factors was studied using the response surface methodology. Based on the optimum parameters, five reusability test was performed for both suspension and spin-coated mode, where 92.89% of MB was degraded in the fifth cycle for suspension mode and 88.21% for spin-coated mode. The photodegradation efficiency of methylene blue, methyl red, rhodamine-B, Congo red, acid blue-25, and methyl orange were 85.84%, 74.62%, 70.53%, 58.66%, 45.21%, and 40.38%, respectively, at a neutral pH. The effect of scavenger and total organic carbon (TOC) were analyzed. Moreover, the degradation pathway was identified using an LC-mass spectrometer. This work showed that slag nanocomposite is effective for dye degradation and lowering the overall cost of the Fenton process at a neutral pH.