Ferronickel slag (FNS) was used to prepare high-quality glass–ceramicsGlass-ceramics with the addition of iron ore tailings (IOT) via microwave-assisted one-step crystallizationOne-step crystallization, with a focus on the effects of crystallization temperatureCrystallization temperature and time on the phase composition, microstructure, and properties of the product. As the temperature increased from 800 to 890 ℃, there were no crystal phase changes of the glass–ceramicsGlass-ceramics despite the gradual precipitation of enstatite and spinel which led to an initial increase and then decrease in uniformity of the microstructure. Consequently, the bending strength and Vickers microhardness of glass–ceramicGlass-ceramics increased firstly and then decreased. By fixing the crystallization temperatureCrystallization temperature at 863 ℃, as the crystallization timeCrystallization time increased from 5 to 30 min, the crystal phases in the resulting glass–ceramicsGlass-ceramics remained unchanged despite their content changes. Meanwhile, the glass–ceramicGlass-ceramics structure became increasingly uniform and denser, improving the Vickers microhardness. Finally, by crystallization at 863 ℃ for 10 min, a high-quality glass–ceramicGlass-ceramics with a density of 3.12 g/cm3, bending strength of 162.4 MPa, Vickers microhardness of 9.2 GPa, acid resistance of 99.81%, and alkaliAlkali resistance of 99.26% was obtained.