Abstract: The blast furnace is divided into two zones of hot zone and solid furnace charge zone.Based on the material and heat balance, according to lager-scale blast furnace production data, the mathematical model of injection of coke oven gas to blast furnace is established.The calculation results show that when coke oven gas injection volume is increased by 50 m³, ironmaking CO₂ emissions will reduce 5%, while theoretical flame temperature is decreased by 35℃.If keep the theoretical flame temperature same as large-scale blast furnace, with the increase of amount of coke oven gas injection, CO₂ emissions of ironmaking are larger than that without considering theoretical flame temperature, but it can always decrease CO₂ emissions obviously.