In China, iron and steel plants are confronted with increased demands to reduce their CO2 emissions. Data on CO2 emissions derived from iron and steel making is a basic requirement for a certificate of CO2 reduction. In the current paper, carbon flows from blast furnace and basic oxygen furnace (BF-BOF) steelmaking systems are analyzed using Material Flow Analysis (MFA). The computation method is built and used to calculate CO2 emissions in three steel works. The amount of carbon flow and CO2 emission per ton of product (EFCO2) of each process in BF-BOF steeling systems is obtained. The results show that the EFCO2 of each process varies significantly. As for the highest percentage of parts, the EFCO2 of the blast furnace iron making is greater than 700 kg on average; however, the EFCO2 of casting is only roughly 50kg. The EFCO2 of the same process is more influenced by the firm size, and the main production equipment scale plays a small role. In the end, the input of coal and coke is decreased by using charcoal instead, CO2 is removed from blast furnace gas along with carbon capture and storage, and traditional energy saving approaches/technologies for CO2 reduction for the iron and steel industry are introduced.