Abstract: In order to study the law of indirect reduction in the process of carbothermal reduction,experiments were carried out on a 20 kg/h pushing boat heating furnace.The changes of gas composition in the process were recorded by on-line gas analyzer,and composition of reduced samples was measured.The influence of coal type,particle size of pulverized coal and preparation method of iron concentrate on indirect reduction reaction was discussed.Finally,the source and quantitative relationship of indirect reduction process were analyzed theoretically.The results show that indirect reduction mainly comes from the chemical reaction between iron oxide and CO produced by direct carbothermal reduction process.During the step reduction process,some volatiles of coal are involved in the reaction,leading to the proportion of CO₂/(CO+CO₂) in the stable gas more than 20%.In a certain range,the smaller size of iron ore concentrate powder achieve better the reduction effect.