A novel technology, modified roasting in CO–CO2 mixed gas and magnetic separation, was presented to recover iron from copper slag. The effects of various parameters such as dosage of flux (CaO), gas flowrate of CO and CO2, roasting tem-perature, roasting time, particle size of modified slag and magnetic flux density on the oxidized modification and magnetic separation were investigated by comparison of the X-ray diffraction patts and iron recovery ratio. The optimum conditions for recovering iron by oxidizing roasting and magnetic separation are as follows: calcium oxide content of 25 wt.％, mixed gas flow rates of CO2 and CO of 180 and 20 mL/min, oxidizing roasting at 1323 K for 2 h, grinding the modified slag to 38.5–25.0 μm and magnetic separation at 170 mT. The mineralogical and microstructural characteristics of modified slag revealed that the iron-bearing minerals in the copper slag were oxidized, the generated magnetite grew into large particles, and the silicate in copper slag was combined with calcium oxide to form calcium silicate. Finally, the iron-bearing concentrate with an iron grade of 54.79％ and iron recovery ratio of 80.14％ was effectively obtained.