Based on the physical and chemical properties of high-temperature iron-containing kiln slag， the online reduction-melting is proposed based on the physical and chemical properties of high-temperature iron-containing kiln slag， the matching law of online reduction-melting and energy matching law of iron-containing kiln slag is studied by using the Factsage thermodynamic software，the changes law in the phase composition of the reduction-melting reaction process are explored，and the appropriate carbon-oxygen mass ratio，heating rate and melting temperature are obtained. The results show that the reactions of iron-containing kiln slag reduction-melting process are mainly the reduction of iron oxides，zinc oxide and zinc ferrite，and the melting content of CaO-SiO₂ -MgO-Al ₂O₃ slag system. It is calculated that the online reduction- melting method could save about 1. 76 × 10 ⁸ J/ t of heat from the treatment of high-temperature iron-containing kiln slag， which not only can reduce coke consumption，but also reduce CO₂ emissions. Under the conditions of carbon-oxygen mass ratio of 1. 4，heating rate of 15 ℃ / min and melting temperature of 1 500 ℃ ，the reduction-melting effect of iron-containing kiln slag is good，and the metal yield can reach 93. 67%.