There are many processes for pyrometallurgical smelting copper ore. The discharged copper slag contains 0.4–4.0% Cu and 20–40% Fe usually. The phase composition of copper slag is complex, the disseminated particle size is fine, and the distribution of copper and iron is very dispersed. In the copper slag, copper component occurs in copper matte phase, and iron component occurs in fayalite, magnetite, iron-containing silicate and other phases, The process of separating and recovering copper from the copper slag is mature, and the copper in the slag can be reduced to 0.2–0.3% Cu. However, iron content in the slag is close to the grade of iron ore. There are many processes to recover iron from the slag at present, but the treatments cost are high and the effect are poor, so far a large amount of the slag is still natural accumulation. The physical and chemical properties of each phase on Cu–Fe–S–O system have already analyzed theoretically. Based on this, the selective enrichment and precipitation of magnetite phase in the slag can be realized by adjusting the parameters such as oxygen potential (PO2), temperature (T) and composition of additive (Ci). The modified slag gotten can be processed by gravity separation, magnetic separation and flotation separation to obtain iron concentrate with a grade of 60.6% Fe.