The sustainable development against global warming is a challenge faced by societies at global level. For steel industry, the pressure of reducing CO_2 emission is likely to last many years. During the past decades, the CO_2 emission per ton steel has been reduced mainly due to the improvement of energy efficiency. Entering the 21st century, the steel manufacturing route must have three functions, namely, production of high performance steel products, conversion of energy, and treatment of waste. In the near future, it is expected that existing BF-BOF and EAF routes will be improved, in order to produce high performance steels, increase the use of scrap, and integrate steel industry with other industries for mitigating CO_2 emission. In the long term, using carbon-free energy, reducing agents, and storing CO_2 securely or converting CO_2 into a harmless substance can be presumed for tremendous reduction in CO_2 emission. The sustainable development against global warming is a challenge faced by societies at global level. For steel industry, the pressure of reducing CO_2 emission is likely to last last many years. During the past decades, the CO 2 emission per ton steel has been reduced mainly due to the improvement of energy efficiency. Entering the 21st century, the steel manufacturing route must have three functions, namely, production of high performance steel products, conversion of energy, and treatment of waste. In the near future, it is expected that existing BF- BOF and EAF routes will be improved, in order to produce high performance steels, increase the use of scrap, and integrate steel industry with other industries for mitigating CO_2 emission. In the long term, using carbon-free energy, reducing agents, and storing CO_2 securely or converting CO_2 into a harmless substance can be presumed for tremendous reduction in CO_2 emission.